Kobold Avenger said:
Though it seemed sort of interesting thing that there could only be 33,333 of each subrace at a time, I felt that at other times it wasn't the keenest idea, though it does explain why they aren't as significant as Demons, Devils and Yugoloths.
You're slightly off on the numbers. There are 3,333 of each type of gehreleth/demodand, for a total of 9,999 in existence at any one time. When times become very tough, then their ranks swell to 6,666 of each type, for a grand total of 19,998, but as soon as whatever crisis it is passes, its back down to 9,999 again.
As for the idea that they were exiled to Carceri, it actually does match up with the idea back in Planescape, where if you leave a larva alone without any of the influences of the Night Hags, Yugoloths, Tanar'i and Baatezu, it will eventually grow into a Gehreleth by itself.
As I recall from
Faces of Evil: The Fiends, that's not how it works for gehreleths (or yugoloths for that matter - new yugoloths are not formed from larva, a new mezzoloth just appears at one of their towers when a yugoloth somewhere else dies (and of course, yugoloths can be born from other yugoloths also). Night Hags, for that matter, just herd and sell larva, they don't come from them). Gehreleths are considered "exiled" to Carceri because they were created on the Grey Waste by the mad baernaloth Apomps; his attempt to duplicate the work of his fellows creating the yugoloths. When his peers saw his creations though, they were outraged at the flawed things, tainted with chaos. Apomps and his monsters went to Carceri (to avoid punishment of destruction from his outraged fellows), and remain there to this day.
As for how they're made, whenever a shator dies, a kelubar is advanced to become a new one. Whenever a kelubar dies, a farastu is advanced to become a new one. And whenever a farastu dies, Apomps just creates a new one from a corpse somewhere on Carceri (and there is always a corpse around on the plane of treachery and lies). No larva necessary.