User blog comment:Johnnybravo44/Comicvine makes me laugh/@comment-61371-20101125005855/@comment-1943608-20101127112325

Fenris and Living Monolith both are mutants. However, Fenris are a special case, as they had mutant genes given to them in utero, and wouldn't have been born mutants otherwise. The confusion with the Monolith comes from him being genetically manipulated by Apocalypse; the Monolith's powers didn't activate naturally, and he'd have likely stayed a latent mutant (one whose powers don't trigger) if it hadn't been for Apocalypse grafting some of Havok's DNA into the Monolith's (which is also why Havok and the Monolith are linked to one another).

Sauron is very specifically NOT a mutant - he's defined as a "non-mutant variant" in his first appearance, which was Xavier's original terminology for a mutate, someone who gains their powers from external cause. Mimic is a mutant; there was a lot of back and forth over it to begin with, and it initially looked like he was a mutate, but now he's considered a latent mutant whose powers got triggered post-puberty. Warlock is a mutant; the murderous way of his species is hard-wired into them, and Warlock lacks that. Additionally, when he was one of the Fallen Angels, one of his teammates was the mutant Chance, who could cancel out or boost other mutants' powers; before she realised this, she kept accidentally depowering her teammates, and when she depowered Warlock he immediately went on a rampage, seeking to slay those around him (and lest anyone say this was just him believing himself a mutant and only thinking he'd been depowered, Chance's powers weren't visible, and Warlock was unaware she'd just depowered him).