The characters that have been claimed so far are as follows:
Sylux - OPEN
Weavel - OPEN
Trace - OPEN
Armstrong Houston - OPEN
Kraid (Super Metroid) - OPEN
Pyonchi - OPEN
Damara - OPEN
Etecoons - OPEN
Dachoras - OPEN
Admiral Dane - OPEN
Bird Grandpa - OPEN
Rundus - OPEN
Noxus - OPEN
Ghor - OPEN
Mother Brain - OPEN
Dark Samus - OPEN
SA-X - OPEN
Rhedogian - OPEN
Anthony Higgs - OPEN
U-Mos - OPEN
Adam Malkovich - OPEN
MB - OPEN
Metroid Prime - Sivus Grahn
Ridley - Sivus Grahn
Samus - Sivus Grahn