How Is Thanos a Deviant Eternal?

In the comics, Thanos is the product of two Eternals conceiving a child, an act that isn't allowed among them. As a result, he becomes host to the Deviant Gene, which alters his appearance but still technically makes him an Eternal.

What makes Thanos a Deviant?

An Eternal getting a Deviant-like mutation was later dubbed “Deviant Syndrome,” or the way Thanos looks with his purple skin and ridged chin. (Of the two sons, he's the only one with this condition; Eros looks like a regular Eternal, something that Thanos naturally hated his brother for.)

How is Thanos a Eternal Deviant hybrid?

Thanos, Marvel's big bad, is an Eternal-Deviant hybrid. His purple skin and scarred face are proof of his Deviant lineage, but the fact that the Mad Titan possesses numerous superpowers – and could wield the Infinity Stones – is also evidence of his Eternal bloodline.