Pyrosphere

The Pyrosphere is a stage appearing in Super Smash Bros. for Nintendo 3DS / Wii U and is based on the location with the same name from Metroid: Other M.

Overview
The main body of the Pyrosphere stage is fairly long aerial platform with a metallic surface. Above it, float four platforms, arranged in a parallelogram shape. These platforms are also metallic, with a strip of green along the side. In the background, there is a flow of lava, but it is unknown if this affects the stage.

On Miiverse, Masahiro Sakurai provided a caption when revealing the stage, which reads "An enemy from Samus's past may appear at any second…" Because of this, some speculate that a character such as Ridley will appear as a stage hazard, but this is unconfirmed. On the April 8, 2014 edition of Nintendo Direct, the shadow of Ridley could be seen chasing Pikachu, though Ridley himself was not directly seen.

Origin
Pyrosphere is a significant area in Metroid: Other M. The stage in Super Smash Bros. for Wii U is based on the area of Pyrosphere, named the Geothermal Power Plant, that Samus Aran would encounter and battle Ridley. This area's appearance in Other M is mostly the same as it is in Smash 4; the bridge that Ridley burns down, the magma-eruption port that Samus destroys to light the area, and the hole in the wall that Ridley creates while escaping are all in their post-battle state in Smash 4, though the hole has been moved slightly to the right and there is another hole to the right of the door for unknown reasons. Also, the four floating platforms of the stage are not present in Other M.

Trivia

 * Super Smash Bros. for Wii U is the second fighting game to feature the Pyrosphere as a stage. Because Team Ninja helped develop Other M, they were able to include a Pyrosphere stage in Dead or Alive Dimensions using the name "Geothermal Power Plant". It resembled the Super Smash Bros. stage, but lacked the floating platforms and featured Samus and Ridley as stage hazards.
 * Consequently, Pyrophere is also one of three stages in the Super Smash Bros. series to be featured as a stage in fighting games outside of the Super Smash Bros. series, the others being Boxing Ring and Green Hill Zone.