D&D General Homebrew Eberron Brainstorm: The Hearts of the Progenitors

[Levistus's_Leviathan]

Hey everyone. Sorry if the title of the thread is a bit unclear. The purpose of this thread is to brainstorm some ideas for a concept that I came up with in my Eberron, which is that every few hundred years or so (occasionally thousands of years apart), the spirits/souls of the Progenitor Dragons choose a Huge or larger Dragonshard to become their "Heart", which increases the shard's power beyond what it should already have for a Dragonshard of that size, and ties it (and whoever possesses it) to the Draconic Prophecy and lets them manipulate it (to an extent). I think I was inspired when I heard of the Heart of Siberys from either an article on Keith Baker's Blog Website (possibly this one), or I just coincidentally came up with the same sort of idea on my own. I'm not sure which it was, as I got this idea a few years ago for my Eberron campaign (which is ongoing, due to a pause in play during the pandemic).

My players' characters came across the Heart of Siberys, which had fallen from the sky in the Shadow Marches, very early on in the campaign, which granted them a piece of the Draconic Prophecy foreshadowing some of the decisions that they could make later on in the campaign, but extremely vague and in a way that only makes sense in context and once the events come up. They claimed the Heart of Siberys (not knowing what it was) for themselves, and sold it to Zorlan d'Cannith from House Cannith East for 5 million gold pieces, which the party used to become famous (and a bit infamous), buy and create magic items (and some magical vehicles that run on Eberron Dragonshards that the party's Artificer designed), and fund their adventuring throughout the campaign. The party only recently discovered what the Heart of Siberys really was, and all that they know about what House Cannith plans to do with it is to create some extremely powerful Eldritch Machine with it, which they believe would be capable of manipulating reality/the future in some way. They also know that they need to get the Heart of Siberys back and restore it to the Ring of Siberys, or else the Ring of Siberys will continue to lose power and more and more invaders from elsewhere in the non-Eberronian Multiverse will be able to get into Eberron.

The party came across the Heart of Khyber earlier in the campaign (also not knowing its true nature at the time), getting a semi-creepy warped part of the Draconic Prophecy from some malevolent entity that was trapped inside the giant Dragonshard (which was Rak Tulkhesh, but they didn't know that at the time and still don't know this bit of information), which was inside the Crypt of the Ebonmother. They know that the Hearts of the Progenitors are important to the plot somehow and that their energy must be used to twist the Draconic Prophecy and world of Eberron in some way, but they're not sure about the extent of their powers (yet), and have been bogged down by some side-quests, some backstory-based quests, and side-quests that are essential to the main plot but grew into something else altogether. Once they finish those up, they're going to go try and get the Heart of Eberron ASAP.

The only Heart that they haven't come across yet is the Heart of Eberron, which is definitely going to be the hardest to get their hands on. It's underground (not quite in Khyber, but near it) and being protected by and experimented upon by a Mind Flayer colony that serves Dyrrn, the Daelkyr of Corruption (the colony appeared earlier in the campaign, one of them searching for the Heart of Khyber, and the other at the crash-site of the Heart of Siberys, waiting for the rest of their colony to come and claim it). The colony will be trying to corrupt the Heart of Eberron with their psychic powers, which, depending on how quickly the party reaches and claims the Heart of Eberron, could have long-term ramifications for the campaign.

Now, for the purpose of this thread. I have the basic ideas for what these giant dragonshards, the Hearts of the Progenitors, will be capable of doing, but I need a bit of help solidifying the ideas into an actual, workable concept that can affect the campaign. Here are my ideas:

• The Heart of Khyber - The spirit of Rak Tulkhesh is trapped in Khyber Dragonshards that are scattered across both Khyber and Eberron, but in my Eberron, this dragonshard has most of his power trapped in it. If this dragonshard were to be destroyed, have most of its power used up, or experimented upon enough, enough of Rak Tulkhesh's power could be released to allow him to recreate his physical formand start to destroy the world. This obviously is not a good thing, and even though the party is level 13 now, they almost definitely could not beat the CR 28 Demon Overlord. Ideas for how this dragonshard's power could be used, besides unleashing a Demon Overlord:
  • If a person with a Dragonmark was exposed enough to the Heart of Khyber, it could corrupt their Dragonmark and turn them into a normal member of their race with an Aberrant Dragonmark, losing all the benefits that their dragonmark granted them before (a Mark of Making Human would just become a Human or Variant Human with an Aberrant Dragonmark, while a Mark of Shadow Elf would probably become a Shadar-Kai with an Aberrant Dragonmark). In the process, they might gain an Indefinite Madness. If the Heart of Khyber is used in an Eldritch Machine, it possibly could be used to corrupt every single dragonmarked humanoid on all of Eberron in this manner. This clearly would be quite bad.
  • If a person with an Aberrant Dragonmark was exposed enough to the Heart of Khyber, it could expand upon their Aberrant Dragonmark, possibly granting them an Epic Boon from the DMG (as Aberrant Dragonmarks have the potential of doing), or possibly allowing Rak Tulkhesh or the Spirit of Khyber to use Dominate Person/Monster on the Aberrant Dragonmarked person. If used in an Eldritch Machine, the Heart of Khyber could grant an Epic Boon to or mind-control anyone on all of Eberron that has an Aberrant Dragonmark.
  • If used in a specifically-built Eldritch Machine and brought to the location of an imprisoned Demon Overlord or Daelkyr, the Heart of Khyber could be used to release this malevolent entity. If fueled with enough magical energy (possibly by releasing the energy inside the Heart of Eberron or through the death of a Greatwyrm Dragon), the Eldritch Machine could possibly be used to release every single Demon Overlord and/or Daelkyr imprisoned in Eberron's Multiverse, bringing about an extremely violent and unrelenting apocalypse.
  • If the Heart of Eberron is consumed, the Heart of Siberys is destroyed/corrupted, and the Heart of Khyber is incorporated into an extremely powerful Eldritch Machine that runs off of the magical energy trapped inside the Heart of Eberron, and this Eldritch Machine is brought into the innermost Demiplane inside Khyber (the plane of existence), this Eldritch Machine can be used to release Khyber (the Progenitor Dragon), having the crust of the world of Eberron crack as the Colossal Khyber escapes like when a Wyrmling hatches from a Dragon Egg, ending the world as every being on the world dies almost immediately. Khyber then ventures out into the multiverse to do whatever she feels like doing (destroy any world on the Material Plane that she comes across, conquer the Outer Planes, murder every god in existence, etc)
• The Heart of Eberron- Just as normal Eberron Dragonshards can be used to create extremely powerful magic items, fuel spellcasting, or power Eldritch Machines, the Heart of Eberron can do all of that without being consumed, but can also do even more powerful feats of magic if used in different ways. For example, magic items that rely on using charges can be used without expending that magic item's charges while within 100 feet of the Heart of Eberron, spells that require material components (even ones that require consumed or expensive material components) don't while within 100 feet of the Heart of Eberron, and the Heart of Eberron can fuel any Eldritch Machine without being consumed. Less mundane ideas for how to use this dragonshard's power:
  • If the Heart of Eberron is shattered into 13 different pieces, 12 of its fragments' power can be used consumed and used to create one Artifact per fragment if using the Craft an Item Downtime option. If the last fragment of the Heart of Eberron is ever destroyed, these artifacts all lose their magic.
  • If the Heart of Eberron is ground into a powder, and a level 20 Spellcaster with 9th level spell slots is within 100 feet of all of the powdered dragonshard, and they have done at least a year of downtime researching the spell, they can cast an Epic Level spell or the Wish spell without any downsides or possibilities of the spell going wrong.
  • If the Heart of Eberron is ground into a powder and then consumed to fuel an Eldritch Machine, the effects of the Eldritch Machine may span the whole world of Eberron. (For example, using this with a Storm Spire could allow a person that is using the Storm Spire to control the weather of the whole planet. Using this for a Spell Sink would prevent magic from being cast all across Eberron, which would be disastrous, to say the least. Or if you used this for a Mabaran Resonator, you could make it so when anyone on all of Eberron died, they would become a Zombie under the control of whomever is using the Eldritch Machine. Erandis Vol would love that last option.)
  • Other examples are listed in the Heart of Siberys or Heart of Khyber listings (such as freeing Khyber, a Demon Overlord, or a Daelkyr). I could use some help with other ideas for using the Heart of Eberron.
• The Heart of Siberys- The Heart of Siberys is probably the Heart of the Progenitor that has the most potential to help the party, due to the fact that the Heart of Khyber is so malevolent and destructive, and the Heart of Eberron requires downtime/foresight in most cases, or relies on using another Heart of the Progenitors to have its most powerful effects. The most obvious option is to allow the Heart of Siberys to bring Siberys back to life, possibly by using the Heart of Siberys as a dragon egg, but that one would probably take more time than the party would have on their hands. Here are some other ideas that don't involve the rebirth of a godlike draconic entity:
  • If a person with a non-aberrant Dragonmark is exposed to the Heart of Siberys enough, it could grant them an Epic Boon or Draconic Boon, reflavored as a Siberys Dragonmark. This could also possibly make them immune to domination effects and protect them from certain damage types (most likely giving them resistance to necrotic and radiant damage like the Nyxborn Supernatural Gift from Theros). Incorporating the Heart of Siberys inside an Eldritch Machine specifically designed for this purpose could affect everyone on all of Eberron that has a Dragonmark in this way.
  • If a person with an Aberrant Dragonmark is exposed to the Heart of Siberys enough, it could grant rid them of the dragonmark and replace it with one of the 13 non-aberrant dragonmarks (including the Mark of Death), possibly allowing the character to choose, or just picking one that fits the best (an Artificer would get the Mark of Making, a Druid would get the Mark of Handling, etc). Incorporating the Heart of Siberys inside an Eldritch Machine specifically designed for this purpose could affect everyone on all of Eberron that has an Aberrant Dragonmark in this way. This would even work on races that can't normally have dragonmarks, but has an Aberrant one, like Warforged, Changelings, Shifters, Lizarfolk, and more.
  • If incorporated in an Eldritch Machine similar to a Dimensional Seal and if fueled by the Heart of Eberron, the Heart of Siberys could completely cut off one Eberron's planes of existence from the world, in the same way that the Giants of Xen'drik did to Dal Quor 40,000 years ago. Doing this would prevent creatures native to that plane from physically manifesting on Eberron and would prevent Manifest Zones from that plane of existence from manifesting on Eberron (getting rid of all already existing manifest zones from that plane). If the Heart of Khyber is destroyed beforehand, this same process can be used on Khyber, permanently sealing it off from interacting with Eberron and preventing all Demon Overlords/Daelkyr and their fiendish/aberrant followers from physically entering Eberron.
  • If the Heart of Siberys is physically restored to the Ring of Siberys, allowing it to orbit the world of Eberron as it did before, the abjuring shield of the Ring of Siberys that prevents travel to or from the rest of the D&D Multiverse into/from Eberron will be restored.

Those are my ideas so far. Does anyone have any thoughts or comments on this? Any plotholes or contradictions with any previously-established Eberron lore? Any ideas on additional uses of the Hearts of the Progenitors? I haven't decided what should happen if all of them meet or are incorporated into the same Eldritch Machine. Any ideas on what that should do? (Possibly allowing the user to reshape the fundamentals of the world/cosmology of Eberron? Or should they just annihilate each other?)

 

[Lyxen]

Very inventive as usual from you, and I like the storyline. I'm not enough of an Eberron specialist to spot contradiction with lore, but I would not worry about that if your players know as much of that lore as I do (I'm only a player in Eberron campaigns, I don't know much of the lore and I still enjoy the campaigns).

After that, I would not worry overmuch about all the possible endings, just let what the party do steer you, because it's impossible to forecast all the possibilities and they will probably surprise you in a good way along the path. I think you have enough clear ideas about what happens if a given heart is destroyed or restored, let your intuition guide you if something a bit unexpected happen.

In any case, it's a campaign that I definitely would like to play in.

 

[Twiggly the Gnome]

Any ideas on additional uses of the Hearts of the Progenitors? I haven't decided what should happen if all of them meet or are incorporated into the same Eldritch Machine. Any ideas on what that should do? (Possibly allowing the user to reshape the fundamentals of the world/cosmology of Eberron? Or should they just annihilate each other?)

Maybe reverse the action of the ancient giant's moon-breaker device, restore Cyra to its orbit, and allow the quori direct access to Eberron again.

 

[Levistus's_Leviathan]

Maybe reverse the action of the ancient giant's moon-breaker device, restore Cyra to its orbit, and allow the quori direct access to Eberron again.

Okay. Which Heart should do that?

 

[Twiggly the Gnome]

Okay. Which Heart should do that?

I was thinking an eldritch machine containing the triad.

 

[Hawk Diesel]

So I am intrigued by a lot of your ideas here. I don't know that I have much insight or recommendations regarding the functioning of the Hearts of the Progenitor Dragons, but I have some questions that may help shape some of your thoughts.

So the first thing that I notice is that based on your descriptions, in your version of Eberron the progenitor dragons are not just a myth, but are in fact a reality and led to the formation of Eberron and its multiverse. So given this, what is the purpose of the Hearts of the Progenitor Dragons? Based on the creation myth in the setting, Khyber slew Siberys, and Eberron sacrificed itself to contain Khyber. While the creation myth doesn't directly indicate it, I've always assumed that the actions of Eberron against Khyber functionally killed them. But that's my assumption. In your game, are Khyber and Eberron still alive? And whether the progenitor dragons are alive or dead, what makes their essence seek out large dragonshards to inhabit? Why do they have to move or find new dragonshards to inhabit rather than stay in one place? If there is some essence of the progenitor dragons that still lingers beyond their demise, what goals are they striving to achieve by inhabiting these large stones?

Another question I have is that if these hearts of the progenitor dragons possess fragments of their essence, why would the essence of Khyber choose to take up residence in the same shard containing Rak Tulkhesh? How would the essence of Khyber itself fit in the same space contained by a fragment (and a large fragment by your description) of the Rage of War? I am assuming that Rak Tulkhesh was contained in the stone prior to Khyber's essence choosing it as its new heart since they move around, and so what effect would that have on Rak Tulkhesh? How might the servants of this Overlord attempt to use the Heart in service of their master? Did Vvaraak know the nature of this large dragonshard and what might it signify that it was found within her crypt?

Additionally, it seems to me that if these hearts exist and can have such an effect on the Draconic Prophecy, where is the Chamber involved in all of this. This seems like something they would be aware of and working hard to obtain the hearts for their own purpose, if for no other reason than to keep such power out of the hands of mortals (I doubt they want to repeat working with the elves to destroy House Vol or do another continental wipe like they did with Xen'drik).

Finally, why would the Heart of the Progenitors only enhance the powers of their respective dragonshard types? If these stones truly contain the essence of the progenitors, it seems unlikely that their powers would be so well-defined. At the very least, from my perspective they would function more like intelligent or semi-intelligent artifacts with abilities that could be accessed even without the creation of Eldritch Machines (though certainly Eldritch Machines might be able to focus those energies to achieve certain additional effects). And certainly they would be something that could be broken up or ground into dust. At least not without some epic magic or another powerful artifact made for such a purpose.

Also, if it is possible for these Hearts of the Progenitors to restore their respective progenitor dragons to life, then why has it taken so long to do so? Do the essences of the progenitor dragons want to return to full life? What might have prevented this from happening in the past? Surely there are some beings who are or have existed that realize this potential, and have tried to bring it about? And if so, then there were likely others seeking to prevent such an outcome. How do these artifacts fit into the greater history of Eberron?

I'm not sure if any of this is helpful. They are some of the questions I would try to answer in my own game, which would then better guide me in terms of how I would want these artifacts to function within the campaign.

 

[doctorbadwolf]

In my own Eberron campaign I’ve got a PC who is on the verge of discovering that the spirit/consciousness of Eberron is still active, and she is going to give the PC a very important piece of information soon about the conflicts of the campaign (basically, the thing that sounds scary actually has to happen, even though it’s part of the bad guys’ plans, but go ahead and stop the other stuff).

Things I’d allow with an artifact like you’re describing…

• Return the Mark of Death, either by bringing back some elves from the dead or by putting it on a new race.
• Stabilize an aberrant mark.
• Restore an undead to mortal life.
• Create or destroy a manifest zone.
• Reverse the Mourning.
• Make a magic item that can bind a powerful entity like a Delkyr or an overlord.

 

[Levistus's_Leviathan]

So I am intrigued by a lot of your ideas here. I don't know that I have much insight or recommendations regarding the functioning of the Hearts of the Progenitor Dragons, but I have some questions that may help shape some of your thoughts.

Thank you for doing this! I already have answers for a lot of these, but some of them definitely need/needed a bit more ironing out. I hope I can satisfyingly answer them below.

So the first thing that I notice is that based on your descriptions, in your version of Eberron the progenitor dragons are not just a myth, but are in fact a reality and led to the formation of Eberron and its multiverse.

Yes, but not necessarily. In my Eberron, yes, the Progenitors did objectively exist, but it's not necessary to the story. If one were to use a similar idea to this one without having the Progenitor Myth be more or less true in their Eberron, they could just play it as a natural process of the universe, just like how the Planes naturally affect the world of Eberron more or less as time goes by. In this case, yes, the examples where Siberys or Khyber is reborn would be excluded, but the Hearts of the Progenitors could function as a plot device just as easily. The Progenitors being real is true in my Eberron (where they are the same core entities as Tiamat, Bahamut, and Sardior), but it isn't necessary to the "Hearts of the Progenitor Dragons" idea.

So given this, what is the purpose of the Hearts of the Progenitor Dragons?

It's a way for the spirits of the Progenitor Dragons to influence the world of Eberron in some way while still being confined to their current states of being (Khyber being imprisoned, Eberron being dormant, Siberys being shattered). The Draconic Prophecy was created by Siberys, so the Heart of Siberys is his way of driving the Prophecy towards his "goal" (protecting Eberron from the Multiverse and being reborn to aid in this). The other Hearts largely exist as a consequence of that. Basically, Siberys chooses a Heart to further the Draconic Prophecy, so the balancing force of the world requires that Eberron and Khyber get to do the same. So Eberron and Khyber also choose Huge or bigger Dragonshards of their type to become their Hearts, which allows them to manipulate the world in an increased manner for as long as their Heart still has its power.

So Khyber gets the opportunity to try and escape her bonds, Eberron gets to try and counter that act and balance out the Eberronian Planes, and Siberys gets a chance to protect the Eberronian Planes from the D&D Multiverse (as Rising from the Last War states that Eberron is inside the Great Wheel cosmology, secluded from the other worlds by the Ring of Siberys).

Based on the creation myth in the setting, Khyber slew Siberys, and Eberron sacrificed itself to contain Khyber. While the creation myth doesn't directly indicate it, I've always assumed that the actions of Eberron against Khyber functionally killed them. But that's my assumption. In your game, are Khyber and Eberron still alive?

In my Eberron, they're still alive, just very, very dormant. If you've read the Heroes of Olympus by Rick Riordan, they're basically as conscious as Gaea is up until the last book, and Siberys is even less lucid than they are (due to him being dead and all).

And whether the progenitor dragons are alive or dead, what makes their essence seek out large dragonshards to inhabit?

In my Eberron, while the Progenitors may be dead or unconscious, they're still basically gods, and so they never truly die or lose consciousness. This tiny remnant of their minds that is still conscious is what allows them to choose a Heart and have a tiny bit of foresight to see how choosing a specific Heart would affect the world. They're just trying to play their cards right and effect Eberron in a way that furthers their agenda.

Why do they have to move or find new dragonshards to inhabit rather than stay in one place?

They don't have to, actually. In my Eberron, the Heart of Siberys has been Siberys' chosen Heart for several hundred years now. It just was floating around in the Ring of Siberys protecting the planet from forces in the non-Eberronian D&D Multiverse. It just recently came into play because it was accidentally knocked out of the sky (major plot point that I won't get into).

If there is some essence of the progenitor dragons that still lingers beyond their demise, what goals are they striving to achieve by inhabiting these large stones?

Changing the Draconic Prophecy to suit their goals. Khyber does it to try and destroy the world and be released from her prison, Eberron does it to maintain the status quo and help life on her, and Siberys does it to prevent extraplanar invasion and to try to be reborn.

Another question I have is that if these hearts of the progenitor dragons possess fragments of their essence, why would the essence of Khyber choose to take up residence in the same shard containing Rak Tulkhesh?

Almost definitely out of a mix of coincidence and scheming. As mentioned above, all of the Progenitors are nearly unconscious, more like forces of the world with a tiny bit of sentience in their current states. Khyber has three things she considers when choosing a Heart, as follows:

1. Is the Dragonshard big enough? It has to be Huge or bigger, remember.
2. Is this the best chance she has at affecting the Draconic Prophecy towards her goals?
3. Is there any way that she can get an edge over the choices that the other Hearts, unbalancing things towards her?

In this case, the dragonshard in which the largest portion of Rak Tulkhesh's power was trapped just happened to be one of the few Dragonshards on/under Khorvaire that was of proper size. Additionally, it was in an easily accessible location (the crypt of a renowned/sacred dragon in the Shadow Marches), and also housed an additional means for her to try and further her agenda. As stated in the first post, if this dragonshard is broken or if its power is used up, Rak Tulkhesh is freed and the world almost definitely ends. Making this specific Dragonshard be her Heart just makes it more likely for it to be shattered for its power or used in an Eldritch Machine, which could end up either releasing Khyber or Rak Tulkhesh. Khyber's spirit would prefer if Khyber were to escape, but would settle for Rak Tulkhesh.

How would the essence of Khyber itself fit in the same space contained by a fragment (and a large fragment by your description) of the Rage of War?

It's not really Khyber residing inside of the Heart, it's more that the Heart is just chosen to be more important and powerful than others of the same size. It doesn't have a problem squeezing more energy into the Dragonshard because it's godlike in power. It doesn't need to cram/squeeze energy into it, it just manipulates the fundamental nature of the Dragonshard to make it more powerful.

I am assuming that Rak Tulkhesh was contained in the stone prior to Khyber's essence choosing it as its new heart since they move around, and so what effect would that have on Rak Tulkhesh?

Yes, Rak Tulkhesh was trapped inside the dragonshard before it was chosen, and has been trapped inside this dragonshard ever since the Demon Overlords were imprisoned at the end of the Age of Demons.

How might the servants of this Overlord attempt to use the Heart in service of their master?

If Mordakhesh had found out (before my party banished him back to Khyber and re-imprisoned him there), he would have tried to break the Heart of Khyber to unleash Rak Tulkhesh. The same applies to other followers of Rak Tulkhesh. However, they didn't know (thank goodness my party didn't give away that piece of information when they were in the Demon Wastes! That would have been disastrous!), and so they haven't come into play yet. If they somehow find out, or if any member from the Lords of Dust were to discover the existence and position of the Heart of Khyber, they would certainly try to retrieve it and probably attempt to create one of the Eldritch Machines that I listed above in order to free Khyber or the Demon Overlords.

Did Vvaraak know the nature of this large dragonshard and what might it signify that it was found within her crypt?

Yes, Vvaraak knew.

Additionally, it seems to me that if these hearts exist and can have such an effect on the Draconic Prophecy, where is the Chamber involved in all of this. This seems like something they would be aware of and working hard to obtain the hearts for their own purpose, if for no other reason than to keep such power out of the hands of mortals (I doubt they want to repeat working with the elves to destroy House Vol or do another continental wipe like they did with Xen'drik).

Oh, they're involved. When the party was on a mission, they met a Silver Dragon member of the Chamber, told her about the piece of the Draconic Prophecy that they found on the Heart of Siberys and where they found it, and she got involved and reported back to Argonnessen to tell the rest of the Chamber. They're involved, and are trying to get their hands on the Hearts of the Progenitors (they want to restore the Heart of Siberys to the Ring of Siberys to allow it to continue to protect the world from outside invasions, want to use the Heart of Eberron for their own purposes, possibly ascending to godhood or become Great Wyrms, and want to safeguard the Heart of Khyber from their enemies).

So, yeah, you're right. They definitely want to keep them out of the hands of mortals, and are helping the party right now.

Finally, why would the Heart of the Progenitors only enhance the powers of their respective dragonshard types? If these stones truly contain the essence of the progenitors, it seems unlikely that their powers would be so well-defined.

Because the Progenitors have their powers and are more or less stuck with them, I guess? I also prefer the idea of mixing and matching the Hearts in specific uses and Eldritch Machines to make different things possible. Khyber is destructive, so her Heart is going to be tied to destruction. The same thing applies to the other Progenitors.

Do you have any suggestions on how else to do it?

At the very least, from my perspective they would function more like intelligent or semi-intelligent artifacts with abilities that could be accessed even without the creation of Eldritch Machines (though certainly Eldritch Machines might be able to focus those energies to achieve certain additional effects).

In my campaign, the Heart of Khyber was sentient, but that was because of Rak Tulkhesh being imprisoned inside of it. The Heart of Eberron will be slightly sentient, but not actually a true Sentient Magic Item in 5e terms. The Heart of Siberys is the least sentient due to the fact that Siberys is mostly dead.

And certainly they would be something that could be broken up or ground into dust. At least not without some epic magic or another powerful artifact made for such a purpose.

They're immune to most types of damage in my campaign. Like, immune to Fire, Acid, Poison, Psychic, Lightning, Cold, Necrotic, Radiant, Piercing, and nonmagical Bludgeoning damage (and the weapon has to be both magical and made of adamantine in order to do anything, and it's resistant to all slashing damage). They also have a ton of hit points. They're not easy to break, but not super impossible, either.

Also, if it is possible for these Hearts of the Progenitors to restore their respective progenitor dragons to life, then why has it taken so long to do so?

Because it's not easy to do so. It requires you to have access to all 3 Hearts, the destruction of one of them (which isn't easy), and for you to use up the energy from the Heart of Eberron, and for you to make a specific Eldritch Machine with the purpose of restoring a Progenitor, and for you to be in the right, hostile environment (the center of Khyber for Khyber, the Ring of Siberys for Siberys). And the Eldritch Machine requires all the right materials, many of them have to be from different Planes of Existence or Manifest Zones, they all require some kind of sacrifice, well over 10 million gold pieces worth of semi-mundane materials, and more.

They're options, but not easy. Now that I think of it, I think it might require something like 13 Great Wyrms or Demon Overlords to sacrifice themselves, as well as everything I already listed for these requirements. It needs to be ridiculously hard, but not impossible. Close to it, though. That's why it hasn't been done before.

Do the essences of the progenitor dragons want to return to full life?

Eberron doesn't (which is why I didn't list it as an option in the OP), Khyber definitely does, and Siberys does.

What might have prevented this from happening in the past? Surely there are some beings who are or have existed that realize this potential, and have tried to bring it about?

That's actually a good idea for a story of a past example! It has probably been attempted before, by the Lords of Dust for Khyber and the Chamber for Siberys, but they failed in some way, possibly through the meddling of the other faction. Maybe even the Silver Flame/Couatls intervened at some point. Or the Giants did, back when they were relevant.

And if so, then there were likely others seeking to prevent such an outcome. How do these artifacts fit into the greater history of Eberron?

Also another good question for a the story of these Hearts. In the OP I hinted at the possibility that something like this is what the Giants used to end the war between them and the Quori. It could also be similar to how the Couatls formed the Silver Flame and imprisoned the Demon Overlords in the first place. Or how the Orcs imprisoned the Daelkyr. Or maybe the Hearts were involved in all of those points in history, with the spirits of the Progenitors nudging the course of history and manipulating the Draconic Prophecy towards their goals, and good barely winning at all of those points.

That's why I like this idea I came up with. It has the potential to explain any and all of those, and lets the party feel like they can do the same if they earn it. Want to destroy a moon? Or release a Demon Overlord/Daelkyr? Rid the world of all magic? Turn all dead people into Zombies under your control? Reverse the Mourning? Cover the world in an endless, giant hurricane? Destroy the world and release Khyber? Just use the Hearts of the Progenitors and the right materials/magic, and you can do any of that.

I'm not sure if any of this is helpful. They are some of the questions I would try to answer in my own game, which would then better guide me in terms of how I would want these artifacts to function within the campaign.

This helped. Thanks a lot. I hope this helps you understand it, too.

 

[Azzy]

Nice!

I'm doing something vaguely similar. My campaign has a McGuffin called "The Amethyst". It's a larger than man-sized Khyber dragonshard that envelopes a Siberys dragonshard within it. An NPC scion of Cannith want to use it to undo the Mourning, while Lady Illmarrow wants to use it to restore her Dragonmark. The PCs are being hired by the Cannith noble (who believes her House is responsible for the Morning) through a representative of Prince Oargev to retrieve the Amethyst (amongst other things). The PCs are being kept in the dark about most of this, as I plan on letting them figure things out little by little.