Savage Mutants were once regular mutants until adolescence. Shortly after, some anomaly causes the mutant to continue to grow. Increasing frustration, and a clouded mind make these mutants run away from the tribe or clan. It continues to grow until it's about twelve feet tall, with arms and legs as thick as tree trunks. It's skin becomes patchy and tough as the hardest bark. Ultimately it's mind reverts back to a childlike state filled with endless rage. A savage mutants body is riddled with scars, and fresh wounds that they seemingly ignore.
Savage Mutants know nothing but rage. They don't fear anything and don't have any semblance of compassion. They don't sleep or rest, and they'll eat anything that bleeds, bones and all. Savage mutants aren't really tool users, they tend to brutalize whatever they're fighting with their fists, and fearsome bites. When not destroying or killing whatever is in front of them, savage mutants are running towards the sun, full speed, all the time.