Reposting what Echohawk provided...
There are a number of individual cavelings in A2, but this extract seems to provide a good overview of their culture, and stats for a typical caveling:
The cavelings have formed their own society within these caverns and live in different caves, one for each tribe. Most cavelings are insane and any children they have had, they have raised insane. Since most of the cavelings come from lawful races, they have reorganized themselves as one people where it is normal to be insane.
Each caveling tribe serves a purpose in the community. There is the tribe of Leaders, who help decide how new arrivals should be treated and direct the activities of the others. There is the tribe of Warriors who practice mock combats and are supposed to defend the cavelings from slavers and go on raids to the safe cell #28b. The Workers build things and gather fungus, water and small insects. The Hunters hunt cave beetles, spiders and the feared cave lizard. And the Thinkers are teachers and priests and help doctor wounded cavelings and make cavelings out of the children.
Insanity is also on a tribal basis with the affliction helping to determine which tribe a caveling will become a member of. For example: Warriors might be homicidal maniacs, while Leaders might be suffering from megalomania. The DM should select the insanities and will find details in the Dungeon Masters Guide, pages 83-84.
The bodies of the cavelings are horribly twisted and distorted, due to Markessa's "improvements" and they are not recognizable as their original race. The DM should determine how a specific caveling has been modified. Some of the changes are useful, such as the ability to climb walls, infravision, clawed hands and so forth, while others will only grotesque. The typical caveling will be AC 10; MV 12"; HD 1, 2 or 3; #AT 1; D rock 1-2 +2 or stone club 1-6+2.
Communiction with cavelings will be difficult, because their language consists of gutteral grunts and shrieks.
When cavelings are first encountered they will be curious, but cautious. If the cavelings reaction is friendly they will try to amuse the newcomers with songs, dances, tricks and by throwing gifts of fungus or smooth stones at them. These actions may appear hostile to the party, but if no hostile action is taken in return, the party will be deemed friendly and they will grab the hands of the characters and drag them to the Leaders' cave.
If the Leaders determine the characters are not the "Messengers of Light" they await, they will welcome them as caveling, and set a feast of fungus, puffballs, spider meat, dried roaches and fermented beetle juice. The beetle juice is very intoxicating and characters imbibing must save vs. Poison or become drunk and slow-witted. Drunk characters will fight at -2 to hit and damage.
There will be much dancing and hooting and then the Thinkers will be sent for to make the newcomers into cavelings. To make a caveling the Thinkers will attempt to surgically alter the form of the character. A character must make a system shock roll to survive the completed operation.
Several encounter areas are provided below with information about certain personalities detailed. The DM should create the characteristics of the other cavelings. The caveling reactions are left to the DM's decision because they are so random and insane.