The Giamarga wrote:Vampyr mummy = over-the-top. IMO they should be antagonists. Note that the slumlord Vladimir Ludzig is either a Ftr6/Vampyr8 or an Ari3/Ftr10/Vampyr8, so he's a force to be reckoned with.
All the more reason to raise some of his lackeys as allies.
Well, we gotta start somewhere.

My vision was that she came back after a decade or two of "worship" by a living cult that doubled as a guild (there was no guild when she passed away). She might have killed the guild to make them into her servants, or she might have reanimated them after they ran afoul of the vampyrs, or any other number of scenarios.
To create an undead guild she has to have the power to power to create more undead, most probably minor/lesser mummies. Probably through an SLA. (This is a bit too similar to Simon Audaire from the great Dragon article The Cult of Simon Audaire btw.)
Any mummy-worship group is going to resemble Simon Audaire.
What kind of Rogue was she in the first place? She must have been "adventuring" to get to such a level of competence.
That's where I got the idea about her taunting Drakov. I'm thinking a 16th level rogue could pull off some hilarious stunts to thumb her nose at the man, and get a huge following doing it.
Then she was entombed alive together with her whole guild in the secret headquarters which happened to be a secret temple to some ancient gods (dark/akiri?).
I don't see any need to bring in a temple to anyone.
Or she herself did bring back an item from such a tomb while adventuring and with that the means that later made her come back?
Possible...
Or was there a mummy who somehow got to Falkovnia and sought to make her his mistress?
I get the feeling that you want to involve more classical mummies, as opposed to the general Ancient Dead. After all, the Lamenting Rake of Paridon didn't have a temple to some forgotten deity, or an item from such a tomb, or an Akiri mummy, and he managed to make the transition.
If you want to involve more traditional mummies, I'd recommend looking into the Falkovnian tombs mentioned in VRGttAD. One of those was collapsed to seal such creatures in, but that's hardly an obstacle to a 16th level character.