As Spiritia Rosenberg (or Grolla Seyfarth) ventures through the hallways at the end of the stage, a beholder resembling a giant floating eyeball follows her, spying on her from outside the palace windows and allowing Iris Sepperin to watch her actions from her residence in her palace ballroom. As soon as she enters the boss room, a huge metal door appears behind her, trapping her inside as the background outside the palace windows turns red, starting the boss fight.
Pieces of the Deviled Egg's body will fly at the player's character, which she has to jump over or slide underneath to avoid. As soon as its body becomes whole, the monster will open its single eye and fire a single bullet at the player's character. The Deviled Egg's weak spot is its eye, which of course opens up on different places of its body quite often, making it hard to hit.
Once half of the Deviled Egg's health is depleted, it'll start changing the gravity every now and then, flipping everything upside down and vice-versa, and the beholder watching from the background will get slightly bigger. Just like the various previous times the player was flipped upside down due to gravity change, her controls will be reversed, making it harder to dodge the Deviled Egg's attacks until the player is rightside up again.
The Deviled Egg's weakness is against Liebessturm, which is obtained from Liebea Palesch. Liebessturm can be used to defeat it in four hits.
Upon defeat, the Deviled Egg's eye will explode and the pieces of its body will fall off and burn away, while the beholder that was observing the fight also burns away at the same time.
- Yellow Devil
- Yellow Devil MK-II
- New Yellow Devil
- Green Devil
- Grey Devil
- Dark Moon
- "Twin Devil"
- Block Devil
- Shadow Devil
- Rainbow Devil
- Lava Demon
- Dark Devil
- The Deviled Egg is very similar to the Yellow Devil boss in the first Mega Man game.
- It also makes a cameo appearance masquerading as the Wind Fish's Egg from The Legend of Zelda: Link's Awakening on Iris Stage 2's custom Game Over screen.