Thanks, that is really helpful.
Did you have any favourite bits?
What I suspect is happening is that the guard who is supposed to come is being created, but is unable to make his way to Xulaye. I'll take a closer look later today.
In the meantime, you *might* be able to use the console. Try this:
Whenever you can during this scene, pause. Then, in the console, type:
CreateCreature("lk#xmg1")
Then, unpause. Hopefully that should be enough to continue.
Hi,
I had the same problem today and creating the creature via console worked, thanks.

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Another problem I found while trying some work-arounds by myself:
I gave the real eggs to Phaere and interjected the ritual attacking Ardulace like Xulaye demanded. Ardulace and Phaere got hostile and I killed them. But after that nothing more happened. I couldn't even leave the room because it's locked by "the might of Lolth" (the game said). I teleported myself to the temple entrance via console but there happened nothing either.