D&D 5E Bag of Beans killed 2 PCs, solo bosses suck, and where to go from here....

[Swarmkeeper]

Does the bag of beans still have any beans left? If so, perhaps the mummy lord knows for certain that two other beans are also mummy lords (or something), who happen to be more powerful siblings/friends/mentors of his. One of his goals could be to locate the PCs to get his hands on the remaining beans. In this way, he hopes to gain some familiar allies in this strange new world he's been awakened into.

Or perhaps to prevent those beans from being used so he has no rivals in his quest for [X].

 

[toucanbuzz]

How long until they plant another one, under the principle of "there's no way we'd get two Mummy Lords in a row"?

Lol, they dumped the bag off a tall tower and said good riddance to it.

 

[MarkB]

Lol, they dumped the bag off a tall tower and said good riddance to it.

Did it land in fertile soil?

 

[Quickleaf]

So yeah, I've got a CR 16 Mummy Lord very confused to be in a forested faery land in possession of a powerful artifact sacred to the gawd of the dead, who HATES undead in this setting. This Mummy Lord is in the middle of the PC barony, a rival monster kingdom about to invade, rival city states that fear expansion of their kingdom, a soon-to-be awakened cyclops lich in a nearby barony's ruins who will resume world conquest on behalf of his long-dead conquering race, and a supreme fey threat yet to be fully unveiled.

So, ideas where my poor Mummy Lord goes and does? I really wasn't expecting this...

You have lots of backstory for your campaign that sounds like fun! Could you find a way to make one of the ancestral dead either of the the PC's land... or the monster kingdom... or one of the rival city states... or related to the "supreme fey threat"... be the mummy? And if those cultures don't have a mummification tradition could you reskin it as a bog mummy?

 

[J.Quondam]

You have lots of backstory for your campaign that sounds like fun! Could you find a way to make one of the ancestral dead either of the the PC's land... or the monster kingdom... or one of the rival city states... or related to the "supreme fey threat"... be the mummy? And if those cultures don't have a mummification tradition could you reskin it as a bog mummy?

Or instead of ancestral dead, what if the mummy actually is one of the current faction leaders... made undead and returned from some desolate future to seek vengeance for something that hasn't occurred yet? So that faction leader exists both in their current form, and in their dessicated mummy form from the future?

 

[Savage Wombat]

Well, how many HP should a mummy lord have to make it a viable challenge for appropriately-levelled PCs?

 

[Eltab]

Even if the PCs dump the Bag of Beans, the Mummy Lord will track it down (and !ater them too). Somebody turned him into a bean - he wants to reverse-engineer that ... and maybe do it unto a particular foe. Plus, are the other beans somebody he can use as a minion or lieutenant or ally?

 

[MarkB]

Even if the PCs dump the Bag of Beans, the Mummy Lord will track it down (and !ater them too). Somebody turned him into a bean - he wants to reverse-engineer that ... and maybe do it unto a particular foe. Plus, are the other beans somebody he can use as a minion or lieutenant or ally?

Also, I hear you can trade them in for a whole cow.

 

[UngainlyTitan]

Well, how many HP should a mummy lord have to make it a viable challenge for appropriately-levelled PCs?

I do not think there is a simple, one size fits all answer to this question. My rule of thumb (based on a blog post by Sly Flourish) is that if the CR of the monster is greater than half the total class level of the party then the encounter is deadly. In that there is a good chance of dropping and or killing a pc or two and an outside chance of a TPK. I have never tpk'ed a party this way and only outright killed characters twice in my current campaign.
However, this only holds up to about level 16 or so where it takes more to kill characters. There is a considerable variation. The factors are: how good are the party tactically? The exact composition of the party, and level of optimisation. Some parties are more vulnerable to certain types of opponent than others. Magic items are a significant factor and larger parties are naturally more resilient both by hp pool and the action economy swings strongly in their favour.
The OP's situation was the result of, essentially a random encounter. Personally I would not throw a CR15 encounter at a level 5 party unless I built the encounter with the party in mind and/or I would be inclined to give them the possibility of not engaging with the encounter.
Although from the description in the bag of beans entry they could have chosen not to go into the pyramid.

 

[hairy stinkeye]

The 60’ base is only the tip of the iceberg. Beneath the ground there is now a massive structure housing an entire necropolis for which the Mummy Lord is only a doorman. The powerful undead within immediately begin drawing arcane power from the feywild forest around them, turning it into barren desert wasteland. Rametep the Lich-King and his army of the dead will soon emerge to lay conquest to the feywild…unless the PCs can stop them.