Special Stages · Stage 3
Aku Studies 401: Field Research
悪魔研究Ⅳ発見
Aku Studies 401: Field Research is a Battle Cats stage in Empress' Report 4. It costs 100 energy and sends 11 enemy spawn lines — led by Le'Solar as the boss — against a 880,000 HP enemy base, and clearing it rewards 8,930 XP. Its enemies carry the Aku, Black, Floating and Alien traits, so cats that target them do the most work here.
Data updated: 2026-08-31
100Energy Cost
8,930XP Reward
880,000Enemy Base HP
4,600Stage Length
12Max Enemies
9.5Difficulty
Enemy spawns (11)
| Enemy | Strength | Count | First Spawn | Respawn | Base HP Trigger | Notes |
|---|---|---|---|---|---|---|
 Sinner Snache | 500% | ∞ | 3.3s | 13.3s~20s | 100% | — |
 Doge Dark | 1000% | 2 | 6.7s | 20s~26.7s | 100% | — |
 Brollow | 150% | 3 | 23.3s | 20s~23.3s | 100% | — |
 Croco | 4000% | ∞ | 33.3s | 10s~16.7s | 100% | — |
| Sinner Snache | 500% | 10 | 0.1s | 13.3s~20s | 99% | — |
| Brollow | 150% | 8 | 0.1s | 23.3s~26.7s | 99% | — |
| Brollow | 150% | 5 | 0.1s | 10s~16.7s | 99% | — |
| Doge Dark | 1000% | 8 | 0.1s | 16.7s~23.3s | 99% | — |
 Tackey | 200% | 2 | 0.1s | 30s~36.7s | 99% | — |
 Le'Solar | 2500% | 1 | 0.1s | — | 99% | Boss |
 Ms. Sign | 100% | ∞ | 900s | 900s | 100% | — |