Avalanche

Avalanche is a member of the Brotherhood of Mutants.

Biography
Avalanche was brought by Pyro to Muir Island as Mystique had a job for them. The duo decided to kidnap Dr Adler for ransom, but it turned Adler was Mystique in disguise. When Mystique explained the real plan to Pyro, Avalanche asked who was that "Apocalypse" they talked about.

Avalanche would re-appear as a member of the Brotherhood during their assassination attempt on Robert Kelly.

Background information
In "The Cure", Avalanche seems not to know Mystique, and Pyro must explain him that she's a shapeshifter. However, flashbacks in "A Rogue's Tale" show him as part of Mystique's Brotherhood before these events.