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The "Acid Worm's room" is a room in Kraid's Lair. It appears in Metroid and Metroid: Zero Mission, with significant differences between versions.


In Metroid, this room is a simple corridor constructed out of blue brick, with two red Air Holes in the floor spawning endless Geegas. These can be shot repeatedly to restore Samus's energy and Missile Ammo. There are also three gaps in the floor that are filled with acid. The room is inhabited by Skrees and one Sidehopper. Near the exit is a floor-mounted pedestal, and two on the ceiling. A large brick overhang exists on the ceiling near the middle.

Samus evades the Acid Worm's attacks.

The room underwent a significant change in Zero Mission, as did the two corridors above it that were once identical. It is now flooded with acid, save for a pair of cube-shaped platforms suspended in midair. The room's architecture is now a mixture of light and dark purple and appears to be of Chozo origin, as there are several hieroglyphs resembling that of their written language within the walls. Additional ruins can be seen in the background. A zip line is integrated into the ceiling, with a switch for it above each midair platform on either side.

When Samus rides along it, the Acid Worm suddenly appears from the acid and begins a boss battle. Periodically, it causes the acid to rise above the level of the lowest platforms, forcing Samus to jump to the higher one. She must also use the zip line to avoid the worm's ramming attack. Once the monster has been defeated, it sinks into the acid, which drains. This reveals a lower floor with a visible gap, which can be opened by using Bombs. This leads to a platform in a lower chamber suspended above acid, with three pedestals on either side. An opening in the left wall leads into a chamber with a Missile Tank.

Connecting rooms[]

In Zero Mission, each door appears to be higher in position from this room than the ones it exits into, when all are viewed together on a ripped map of the game.



Zero Mission[]

Official data[]

Metroid: Zero Mission: The Official Nintendo Player's Guide[]

Page 45
"Open the new hatch and enter the next area. The acid worm will appear after you slide to the left side of the large room.
Acid Worm
"When the worm emerges, stand under the ceiling mechanism while facing away from the creature, wait for it to wiggle its appendages, then jump straight up. After you ride to the other side, pelt the monster with missiles.
Once you've hit the beast several times, the acid level in the room will rise then fall. Seek higher ground. If you go to one of the edges of the room, the creature will fire projectiles at you when it pops out of the lava.[sic] Hit the projectiles with your beam for energy and missiles."
Page 46 (Missile Tank)
"Following your defeat of the acid worm, use bombs to blast your way to the room's lower reaches. Jump left over the acid, then fire at the left wall to open an unmarked room that holds a Missile Tank."