Collaboration Stages · Stage 1
Immortal Allen O'Neill
オニ軍曹 アレン・オニール
Immortal Allen O'Neill is a Battle Cats stage in Metal Slug Defense. It costs 30 energy and sends 11 enemy spawn lines — led by ALLEN O'NEIL (Enemy) as the boss — against a 10,000 HP enemy base, and clearing it rewards 4,230 XP.
Data updated: 2026-08-31
30Energy Cost
4,230XP Reward
10,000Enemy Base HP
4,500Stage Length
5Max Enemies
1.2Difficulty
Enemy spawns (11)
| Enemy | Strength | Count | First Spawn | Respawn | Base HP Trigger | Notes |
|---|---|---|---|---|---|---|
 MARS PEOPLE (Enemy) | 100% | 5 | 6.7s | 16.7s | 100% | — |
| MARS PEOPLE (Enemy) | 100% | 1 | 30.7s | — | 100% | — |
| MARS PEOPLE (Enemy) | 100% | 1 | 33.3s | — | 100% | — |
 MARCO (Enemy) | 100% | 1 | 60s | — | 100% | — |
| MARS PEOPLE (Enemy) | 100% | 1 | 80s | — | 100% | — |
| MARS PEOPLE (Enemy) | 100% | 1 | 84s | — | 100% | — |
| MARS PEOPLE (Enemy) | 100% | ∞ | 100s | 20s~40s | 100% | — |
| MARS PEOPLE (Enemy) | 100% | 3 | 0s | 20s~40s | 90% | — |
| MARCO (Enemy) | 100% | 1 | 0.1s | — | 90% | — |
 ALLEN O'NEIL (Enemy) | 100% | 1 | 0.1s | — | 90% | Boss |
 Ms. Sign | 100% | ∞ | 900s | 900s | 100% | — |