Cost of the 1st level:
CRP 2 Huge pit that collects various acids and other dangerous chemicals produced by xerjs. Those acids are then used as one of the strongest xerjs weapons, but it also helps mutating captives of other races into loyal Swarm minions. Acid pool is required to produce powerful xerj warriors and to hire mutants. So, after developing the Regeneration evolution, each level of the pool improves its armour damage reduction effect for defending хerjs by 1.5%.
Comparison by level
| Lvl | Regeneration upgrade |
| 1 | 1.5 % |
| 2 | 3 % |
| 3 | 4.5 % |
| 4 | 6 % |
| 5 | 7.5 % |
| 6 | 9 % |
| 7 | 10.5 % |
| 8 | 12 % |
| 9 | 13.5 % |
| 10 | 15 % |