I also think it would be neat if there were some sort of domino effect were in place where killing off one tribe would set off a chain reaction. Though the tribes are ultimately trying to destroy one another, the harsh conditions of the region have made them interdependent on one another.
The yellow men have a monopoly on potable water, but in order to defend it they have had to give up their hunter-gatherer lifestyle. Now they depend on trade with other tribes in order to obtain food.
That other tribe is in turn dependent on yet another tribe for survival.
This can't go on forever though. I just rolled up the yellow tribe. There's 104 of them. Their section of the dungeon is over-populated. Maybe every tribe has a straw. Which one will break the camel's back?
*edit*
Here's the yellow men's part of the dungeon by the way.
I'm going to make each tribe's section separate then composite them all together.
1. 60' wide pool of pure water in a 100' wide dome.
2. doors
3. 40'x40' chamber with furniture
4. doors
5. 40'x40' chamber with crude barricades made from rubble, a trap door, and a ladder down
6. doors
7. 40'x40' chamber with fountain
8. doors
9. 40'x40' chamber with fountain
10. stairs down
11. door
12. 60' wide bridge over an irradiated river. The river passes through some sort of filtration system on one side
13. ladder up to the surface
14. 20x30 chamber with a raised platform
15. door
16. ladder down
17. 20x20 chamber with a statue of Dagon
18. door
19. 20x30 chamber with a sacrificial pit.
Population:
54 level 0 noncombatants including children
36 1st level fighters armed with spears and stone axes
9 3rd level fighters with iron axes and shields
3 subchiefs (4th level fighters) with swords, shields, and chain armor
1 chief (5th level fighter) named 'Exalted Arbiter' with bastard sword and plate armor
1 shaman (3rd level sorcerer), 'Jibbering Joy-Giver of Winter' with leather armor and a dinosaur-bone club.
Monetary treasures:
1300 platinum pieces in sacks guarded by poisonous insects
30 gems in a chest with a poison needle in the handle
Technological treasures:
Vial of growth hormone
Vial of spider-climb mutagen
Vial of insect control pheromone
All of these are stored in an iron trunk guarded by poisonous insects. Those who drink from these vials must make a saving throw vs. poison or develop a permanent secondary mutation.
Sorcerous treasures:
The tribe's shaman has a piece of ivory with the ritual 'Conjure the Squamous Worm of the Pit' carved into it.