Okay, 100th level module proposal.
First thing is first, the first chapter of the module is for 20th level characters. I figured out a way to use normal high level characters in a 100th level adventure, so you can use it as part of your current game, you’ll see.
Chapter one - the Gods in peril
The story starts with the party receiving a warning from there Gods so strong that it wakes your character, whether you are sleeping, in a coma or even from the grave. A wizard and cleric of surprising power have evaded the premonitions of the Gods by plotting and planning events for a powerful magical event. They evaded the divine power of the Gods ability to see into the future by planning for this event at the base of the Spire in the Outlands where the God cannot see. They have climbed to the top of the Spire and began their magical event by creating a Burning Eye of Al-Ghautra. For those of you not familiar with Magical Events, see chapter 3 of the DMGII.
The Burning Eye of Al-Ghautra is just the beginning, but they have also started a new magical event, an Elemental Swarm (new one I made up for this adventure) that prohibits magic from those not protected in a certain way, and as it is a unique event, only the wizard and the cleric have this power, not even the Gods understand it. The top of the Spire is also the site of a circle with the Spirit of Nature’s Rage. The burning eye is slowly growing, so those who teleport to Sigil find the city in flames and also discover that the Lady of Pain is occupied trying to hold the city together from the vast amount of magical energy forming on the Spire tip.
No way can be found from Sigil to get to the top of the Spire, you have to go to the Outlands and travel from the outer most part of the plane towards the center to the Spire. Every God is concerned and has called a truce of sorts, so every race is represented and all of the Gods have gathered in the Outlands to try and come to a solution. The progressive failings of magic as you get closer to the Spire means that most won’t get to close and most of the Gods will not come closer than 301 miles from the spire as they will lose their divine ranks. A few will deem this threat powerful enough to venture to the top of the Spire itself, however.
Once the party over comes the problems to get to the top of the Spire, should be fun without magic, a third magical events begins. The party sees the wizard and the cleric standing under the Burning Eye of Al-Ghantra on either side of a Sphere of Annihilation . There may or may not be an encounter where the evil doer’s can monologue and/or fight, but before the party gets to crazy, the wizard and cleric complete the next magical event and open a Consuming Vortex of Traal right behind the Sphere of Annihilation. The area if flooded with Negative and Positive energy. Once a few of the Gods enter the area, something unexpected occurs, the Magical event of the Elemental Swarms falters and an Elder - Mega Xag-Ya and an Elder - Mega Xeg-Yi, (energons page 168 of the MotP), enter the area and once they see each other they converge on each other and explode, causing the wizard and the cleric to lose control of the Sphere of Annihilation which gets sucked into the Consuming Vortex of Traal and then pulls in the Burning Eye of Al-Ghautra, causing a massive explosion across the cosmos.
Confused yet? It really isn’t that complicated, just sounds like it.
Chapter 2 - Strange Days
The party is flooded with power, both from the Gods and the energy of all the planes combined. Basically they are recreated, atom by atom, but on the plus side, for the time being, they have the power of 100th level characters, yeh

. They can also temporarily be a different race, remember they are parts of many different races, but no divine ranks. Now they make their 100th level character. Please no leadership feats

The Wizard and Cleric were trying an experiment but with the Gods interfering, they created a rift in the cosmos and destroyed the whole of the current cosmos, throwing everyone, or mostly everyone, into an alternate cosmos.
Adventure hook, you must figure out how to reverse the effects of the Magical Event and restore your old Cosmos or have the deaths of a googolplex beings on your conscious. Deal with that. Parts of this chapter can deal with some fun differences between the old Cosmos and this one, like some old enemies are now your friends and your best friend is a back stabber.
Chapter 3 - The Ajah Armory
As a 100th level guy, you have the same gear you did when you were 20th level, plus a few extra items, but we will have rules for continuing to pimp out your current 20th level gear, this will reduce the massive power or way to much disposable income of a 100th level character, some anyway. Also, you will have access too The Ajah Armory. In this chapter you have a run in with Ay-Gax, a small child, is wondering around the planes, or other location. He is really the Xag-Ya, but he does not know it, and the party should not at this point either. He is healing the sick and curing maladies in Limbo and forces the demons and devils to stop the blood war. He eventually teleports to Sigil
The Ajah Armory
Created under the working name of
recursive co-terminal multi-functional all terrain interdimensional closet of useful things by Mizledorf, the Patron Saint of Gnomes Everywhere, Founding Liege of Kirpah Nasmong- a Gnomish Utopia (Male Celestial Gnome/Bard 33, Illusionist 33, Tinker 33/N). One day Mizledorf realized the name was too long (everyone else would just tune him out when he started to say "recursive"), and he said "Ah hah!" with great triumph. However, his yiddish accent made it sound like "ajah!" And thus his culturally bankrupt allies dubbed the armory the Ajah. Convinced it was flawed, Mizledorf gave it to his friends (the 100th level party) as a gift, and set about improving its design. That's Mizledorf for you, one parts gnome, two parts perfectionist.
How it works: Once attuned to the Ajah, a character need only concentrate as a standard action and whatever piece of equipment they desire appears equipped on them. They make a requisition check: d20 + Concentration. The check is made against the purchasing DC of the requisitioned item. Items worth 35,000 gold or less (DC 40) have no effect on the Ajah. Items (or collective "purchases") worth more cause the Ajah's new wealth to decrease until said items are returned. The wealth loss for a single requisition equals = 1/3 (purchase DC - wealth bonus) rounded up. The Ajah has a base wealth bonus of 40.
Chapter 4 - Iy-Xeg
Iy-Xeg is the Xeg-Yi in human form and he has just slew an epic dragon and is picking through the remains with a stick, like a creepy kid would a dead cat. The PCs encounter him starting an over throw of the heavens and other such suggested encounters for the DM. He eventually teleports to Sigil.
Chapter 5 - The Wizard’s madness
Originally Posted by Philip
Unknown to the players when they try to teleport they are thrown into a dream plane of the Wizard’s mind and has split up into multiple personalities who are battling each other across his own mindscape. Unknown to them the PCs are pulled into his mind and must battle the personalities across an ever-changing landscape.
Without warning the PCs are suddenly the only living creatures left in an utterly barren universe. They have to find out what happened. Perhaps one of them did it inadvertently or they have a traitor amongst them?
The Cleric saves the party at the last minute, as she is trapped in here as well, but not before the PCs have many tribulations and trails.
Chapter 6 - the Cleric redemption
The Cleric knows that things have gone wrong and wants to help make things right, but the Gods don’t know this and they have surprises in store for the cleric, and now the PCs.
Originally Posted by Ozmar
I think this is a good time to introduce the Gods for the PCs to fight and also to have them face mass assaults from armies and such. A good chance for them to really flex their massive abilities by slaying hoards of demons and devils and angels and undead and whatever else we choose.
Chapter 7 - The Lady of Pain’s Revenge
The child incarnations of the Energons have been playing with the PCs throughout the module, playing tricks on them and healing their enemies and starting fights. They are pure energy from the positive and the negative plane and have no emotions, they are, for the first time, free to experiment and they are very good at it, whether it is stopping the blood war or killing all the angels in the heavens, they are just children having fun, without a peer or parent to stop them.
If the PCs attack them, consider them only to have 6 in all stats, but they have the knowledge and power of 1000th level characters, and can cast any spell, including epic spells and they don’t need others to do a ritual with them, so, even if they die, they come back in a single round and can and will use a powerful effect on the PCs. Most of the time however they just act like children, carefree and only thinking of themselves. It should also be noted that bringing the two together simply won’t reverse events, in fact, it gives them purpose. Where before they were content with minor experiments, now they feel whole when together (remember, alternate cosmos, things working backwards) and they begin to terrorize the cosmos.
The Energons are now in Sigil and the Lady of Pain has forced the PCs into Sigil to deal with them. Whatever happens, the PCs must fight the Lady of Pain, even if it is only for a few rounds. She will most likely overwhelm them, but the PCs might get the jump on her, either way she forces or begs the PCs to act and get the Energons out of her city. The Energons are not willing to leave such a fun city, unless the PCs can find a new place for them to have fun.
From Sigil, you can see the massive castle of the Wizard and Cleric that has formed in the center of the ring of Sigil. Actually, all you can see is a giant black sun which seems to absorb light, and everything else, it is a very large sphere of annihilation growing from the top of the Spire. It is so massive that it can almost be reached with very tall ladders from the streets of Sigil, no wonder the Lady of Pain is so upset.
Chapter 8 - Crating the Epic Spell of Reseeding
One of the places the PCs can offer the Energons to play in is the Observatorium. From here, and also with the help of the Library of Lore (Boccob’s Library), the PCs can create an Epic Spells to recreate the cosmos. While there are hard at work, the PCs can slowly see the warriors of the Ex-Blood War slowly taking control of the cosmos. The demons and the devils, without wasting energy on each other, have grown very powerful, enough of a challenge for 100th level PCs and from time to time they try to invade the Observatorium, or wherever the PCs are.
Chapter 9 - Assault on the Castle in the Void
Basically, everyone seemed to like the storyline by Turanil but I wanted something that made everyone happy, so while it may have to be scaled down a bit from your original idea, here is where you get to add your castle/dimension/epochs thingy. The wizard and the cleric however are in the castle, not just a Chronomancer, but the wizard can be a Chronomancer in addition to a wizard

. Note, the Castle in the Void is actually inside a sphere of annihilation, which should make for some great fun in-and-of-itself. Also, the PCs must face the Lady of Pain and get her to let the Gods in the city so they can temporarily open a way into the sphere of annihilation.
Once the cleric and the Wizard are defeated, and they can and do summon some terrible stuff to deal with the PCs, the PCs can then place the energon children at the center of the Castle in the Void and cast the Epic Spell to reseed the time stream. Pretty much the end at that point.
What do you guys think?
Here is the rest of Turanil's idea:
Synopsis: A Chronomancer* (who was but 20th level), using wishes and chronomancy spells, created major time paradoxes which resulted in himself becoming a demi-god, but also creating a mess of dimensions and epochs. Now (inspired from the Amber novels), he resides in a castle at the junction of four planes and a dozen timelines. The world is slowly destroyed by this mess however, and is going to be soon obliterated in a giant sphere of annihilation (due to the time paradox and what not, this sphere is now growing fast, and if not stopped soon enough will devour the planet).
So the PCs will first have to figure out what happens, then get to the mighty castle at the junction of planes and epochs. Of course, other epochs mean they will have to fight villains from the future (with modern weapons) as well as from the past.