I was working on the ape men colony in the Black City's ruined arena, and had some fun with worm madness and the ape men. Here's the simple version so you don't have to go back and read stuff from a year ago:
The ape men were slaves of the aliens in the city, white haired hominids like the Australopithecus, created for labor and servitude. The aliens bred them by devolving early humans down along the genetic tree to a more primitive state. The other factor to consider is worm infection. The Greys bioengineered a parasitic worm that mutates and enrages its host (roid worms)- if you want a blast from the past, here's a whole article about worm infection: Worm infection and berserkers. So what happens when a white ape gets infected with worm madness?
Angry Mutant Apes.
When the ape men see first signs of infection in a member of the band, they dump them in the pits, a series of warren-like passages beneath the tunnels where they lair. There's a ramp leading into the arena from the pits, with a grate barring the way, and the ape men lift the grate to release the hungry mutants whenever the area is invaded. I figure it's like Barsoom with snow and ice.
Angry Mutant Ape
AC as leather armor and shield, MV 12, HD 4, Atk 2 claws, 1d4/1d4, and see below, ML 7, AL N.
The ape men have learned to avoid infected water sources like the well in the Transit Tunnels, but there are still pools on the level 2 Warrens that have worm infection. When a white ape is infected with worm madness, the unstable DNA of the ape men combines with the worm infection to transform the white ape into an actual 4HD carnivorous gorilla monster; 50% of them mutate further and gain one of the attributes from below.
1 Extra Arms - the mutant ape can make 4 claw attacks instead of two
2 Horn - a huge horn grows out of the mutant apes skull, granting a gore attack (1d6)
3 Vicious Bite - the mutant can bite for 1d8 damage
4 Oversized (extra HD) - the mutant is 5HD instead of 4HD
5 Sharp Claws - each claw attack is 3-6 damage (1d4+2)
6 Fast Healing - the mutant regenerates 2hp per round
7 Purple! - 8HD and fist pounds that do 2-12 damage per fist
8 Gore slathered: AC as unarmored, +2 attack/damage, morale 12, roll again
9 Super Intelligent: has used low level telepathy or empathy to turn the other mutants into its followers
This table can easily be expanded. What's your favorite ape mutation that belongs on the mutant white ape table?
* The picture is a mash-up of Trek, Congo, and the four-armed white apes from the Jon Carter Movie.