A piston is a component of various pumping or engine systems in the Metroid Prime series. They are commonly found in the areas explored by Samus Aran as obstacles, involved in puzzles, or are simply part of the room.
There are three rooms in the series containing the word "piston" in their name: Piston Tunnel (Chozo Ruins), Piston Cave (Alinos) and Piston Hall (Eastern SkyTown, Elysia). Pistons play a role in the former two rooms, while a rotary hatch exists in the latter.
Certain Morph Ball tunnels, such as the Piston Tunnel and Piston Cave, feature slowly rising and falling pistons that Samus can roll on top and use as a makeshift elevator. Some pistons are positioned above Samus and will cause damage if one slams down while she is under it, (Metroid Prime) or kill her. (Metroid Prime Hunters) The pistons in the Piston Cave make traversing the room particularly difficult as they can easily knock her to her death in lava, or crush her.
Air-circulation pistons are found in maintenance tunnels in Substation West and East in Base Sector Zero, Norion. These pistons have a flat, rectangular surface and push forward horizontally at intervals of five seconds. Because the heated energy coils in the floor are exposed, Samus needs to navigate the room using the tunnel in Morph Ball form. She must carefully time it so that the pistons do not push her onto the coils. The pistons will telegraph when they are about to pump, as they will flash for two seconds before they push forward. These pistons are powered, at least partially, by turbines in each Substation.
Reactivating the G.F.S. Theseus enables a rising and falling piston in the tunnels leading into the ship. Samus must time her Bomb-Trick or Spring Ball and Bomb correctly while the piston is retracted. This allows her to access the Theseus roof and find a Missile Expansion.
Two pistons are present in the maintenance tunnels of the Steambot Barracks, and appear to be for energy generation. One of them is malfunctioning and does not extend all the way, but the other slams up and down, impeding Samus's progress and damaging her if it extends on top of her.
Samus uses pistons as a Morph Ball lift when descending into the maintenance level of the Aurora Chamber on SkyTown, and into the Podworks underneath the Spire Escape Pod. Both pistons will also bring her back up when she is done repairing circuit boards in these rooms.
Fedtech Plasma Generators in Base Sector Zero are powered by a large piston, which inserts into the platform in the center of all three Generator rooms to power the Defense Cannon. The generators are offline and the pistons retracted when Samus enters the rooms. After Samus uses a security lever at the back of Generator A, the piston will stall, and she must engage its override by using a Hand Scanner. However, in Generator C, the piston will stall, forcing her to manually dislodge them by navigating a complex tunnel system to reach a Bomb Slot on the piston.
In the Auxiliary Dynamo room of Bryyo Thorn Jungle, the exit is blocked by indestructible and non-removable wires. To bypass them, Samus must navigate a Morph Ball tunnel in the wall, but there is a piston blocking her path. She can remove it in bipedal form using the Grapple Lasso. Once she has, she can roll on it to have it automatically lift her higher in the wall, so that she can reach the exit.
Piston structures exist in Hub Access and Transit Tube B in Eastern SkyTown, as well s Western SkyTown. They appear as tall cylindrical structures in the center of the room, with flashing lights moving up and down the shafts. These pistons produce energy that supplies power to the engines of the Sky pod.
During the battle with Gandrayda, she will open the shutters of the Proving Grounds when she has lost 75% of her energy and expose the room to the Acid Rain. Black and blue pistons rise from the floor, but their purpose is unknown.
- Auxiliary Dynamo (default)
- "Piston is stuck in place. Enough physical stress could temporarily pull it down."
- Auxiliary Dynamo (pulled)
- "Piston has been lowered. Upper section of maintenance shaft is now accessible."
- Air-circulation pistons (Substation West/East)
- "Air-circulation pistons are activated and on automatic. Pump interval at five seconds."
- Generator piston system (Generator C)
- "Generator piston system active. Piston is in place and secure. Ready for generator activation."
- Piston structures
- "Piston structure produces energy that is used to supply power to the pod engines."
- Main Cavern (Mining cannon)
- "Piston extends while the mining cannon is firing the beam that cuts through Phazon."