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The current title is not an official name.

The "Serris arena" is a room in Sector 4 (AQA). It appears in Metroid Fusion.


The room appears to be set in a large, square tank. It is half-filled with water, which appears to be somewhat cloudy. Cylindrical tanks of varying size extend into the background; their purpose is unknown, but it is possible that they channel water throughout the sector. Each of them taper off at their ends with a trapezoid-shaped spout. The background has a dark purple hue, while the walls, ceiling and floor are dark green in color. Along the walls and ceiling are ladders, which become useful in the ensuing battle. A bridge above the water, which is initially intact, partially crumbles into the water, leaving four platforms resting on the surface when the battle begins.


Samus enters the room in search of Serris, a specimen that she has been authorized to terminate as it has been infected by the X Parasites. Eerie music begins to play as soon as Samus steps inside. As she exits the water and begins to walk across the bridge, parts of it collapse when she nears the end of the bridge. She must quickly run to the end to avoid falling back into the water. Serris appears a few seconds later, commencing the fight.

Serris weaves its body across, underneath and between the platforms, forcing Samus to make careful use of the ceiling ladder to avoid most of its movements. This becomes especially dangerous as she fires at its head, causing it to engage its super-speed ability and become invulnerable for a short time. If Samus falls or is knocked into the water, she must quickly climb out using one of the wall ladders, as her movement is hindered without the Gravity Suit.

After defeating Serris, Samus can absorb its Core-X to regain her Speed Booster ability, and leave the room. There is little reason to return to it afterwards.

Connecting rooms[]

The room is entered from a tall shaft with a wall divider, which is connected to the breeding tank. It exits into a corridor with leaking water tanks in the background.



Speed Booster
Regained after defeating Serris and absorbing its Core-X.

Official data[]

Metroid Fusion: The Official Nintendo Player's Guide[]

8. BOSS BATTLE (pg. 37)
"Serris swims swiftly through the water of its big tank and jumps high into the air. After you awaken the creature, drop down and look for a safe spot, face the middle of the tank, crouch and charge up your Beam. When you have a clear shot of Serris's head, release the Beam. After a direct hit, Serris will glow white and tear around the tank in a rage for a few moments, during which it will be invulnerable. Wait it out and prepare for another shot. Once Serris is gone, you'll fight a Core-X for the Speed Booster."

Metroid Prime and Metroid Fusion: Prima's Official Strategy Guide[]

This guide incorrectly suggests that Serris' head cannot be damaged with Missiles. This is not true.

Page 102
"Go through the hatch, jump up to the ladder, and walk across the tiles that stretch across the tank. As you near the end, the tiles begin to crumble. Leap across to the right and take a position on the top rung of the ladder. Although you may be knocked off this spot during the fight, you must return here immediately, because it is the only vantage point for landing accurate hits on Serris.
The giant snake zooms back and forth and up and down as it scrapes against the ladder. You must use charged-up energy beams (missiles won't work), so keep your finger on [A] at all times. This way, you can release a maximum beam when Serris comes into range. The only hits that cause damage are head shots. The easiest shot is when Serris is moving toward Samus, but you can also connect when the snake is moving away (as pictured). When you score a hit, the snake turns white and accelerates to super speed. Don't waste your time shooting until Serris slows down.
When the snake finally explodes, a Core-X remains. It is difficult to stay on the ladder when fighting the Core-X, but you can still shoot effectuvely from the tank. Keep moving to avoid the Core-X, and simultaneously pump it full of missiles. When you destroy the Core-X, only the pure X remains. Jump up to the tiles and leap up to capture it, giving Samus a new Speed Booster ability."