Methanosian

Methanosians are a floral sapient species from the swamp planet Methanos.

Biology
Methanosians are descended from carnivorous swamp plants, but evolved into plant-like herbivorous humanoids at some point in their evolution. They can break down rotting plant matter in their stomachs to produce flammable methane that can be used for their fire attacks.

Early Evolution
Methanosians undergo a metamorphosis process that results in them "blossoming".

Abilities
A Methanosian appears to amalgamate the abilities of a Pyronite and a Florauna, being able to manipulate both plants and flames. They are strong enough to push down a large Highbreed weather tower. They can also reattach and regenerate missing body parts.

Omnitrix Transformation
The Omnitrix's Methanosian representative is named Swampfire, who first appeared in the Alien Force episode "Ben 10 Returns: Part 1". Swampfire has appeared in almost every subsequent series except the reboot.

The Ben Tennyson of Dimension 23 has an equivalent of Swampfire named Mr. Mucky, who was confirmed to exist by unused artwork from Omniverse.

Swampfire has also been used by Albedo, Vilgax's Bioid army, and Anur-Mirrored Ben.