HFS being demons, of course.
To summarize what I know:
1. According to the wiki, underground depth 5:5 + FLIER makes a creature participate in the initial wave. 5:5 but no FLIER tag means the creature wanders around in Hell, essentially using animal AI.
2. If no UNIQUE_DEMONs are generated during worldgen, Dark Tower civilizations are disabled. (Dark Tower civs MUST be led by a demon, using another religion type crashes world gen. Likewise, demon led civs MUST be Dark Tower civs, specifying no religion on a civ with another site type also crashes world gen)
3. UNIQUE_DEMONs and regular DEMONs are generated in an annoying way: Approximately the first 1/4 of demon types will be DEMONs, the next 1/4 will be UNIQUE_DEMONs, and the final 1/2 are DEMONs again. If 1 demon type is generated, it will be a DEMON, if two are generated, the first is a DEMON and the second is a UNIQUE_DEMON. Four types leads to DEMON-UNIQUE-DEMON-DEMON. 22 types leads to 1-5 being DEMONs, 6-9 being UNIQUE_DEMONs, then 10-22 are DEMONs again (so it's not perfectly 1/4 1/4 1/2
).
4. It appears that UNIQUE_DEMONs may be unique in their entity type, but not in the world. In my case, I have 2 Dark Tower entities: Moblins and evil Twili. Having 3 types of UNIQUE_DEMON resulted in 3 moblin civs and 1 Twili civ (the max). Having 1 type of UNIQUE_DEMON resulted in 1 moblin civ and 1 Twili civ, both led by instances of the single unique demon type.
Questions I have:
1) Is there really no way to specify our own UNIQUE_DEMONs through the raws?
2) If there are no DEMONs generated, but there are creatures in the raws with 5:5 depth and FLIER, does the initial wave upon opening Hell still happen, or is it disabled?