Any Death Battle combatant who is not of the main "race" or who does not originate from the main planet of their respective series.
Pages in category "Aliens"
“ The Predacons are a race of ancient Cybertronian beasts. Originally led by the one called "the...
“ The Predacons of the G1 Dreamwave comic are a sub-faction of the Decepticons founded by Starscream.
Predacons (G1 Dreamwave comic)
“ The Six Clan is a clan of Six Changer ninja—all of its members are Transformers who have six...
Six Clan (Transformers)