Lava Mountain is the third standard level of Sonic Runners, which would start appearing after reaching Episode 17 of Story Mode.
Based on the level of the same name from Sonic Lost World, Lava Mountain is set in a fiery landscape with magma flowing from the level's many volcanoes. While all characters could play on this stage, it was a Power Type stage, and contained obstacles suitable for Power Type characters such as Knuckles.
The level's most prominent obstacle would be Super Badniks; black Badniks that have harder bodies that make them indestructible to attacks from Speed and Fly Type characters.
Of all three standard levels, Lava Mountain is the only one of the three which was not used for a special event.