Mutation

Fused Zamasu's Mutation is not a transformation that the user seeks or trains toward. It is a consequence of a fundamental contradiction within his being. When Goku Black (a mortal body inhabited by Zamasu's soul) fused with Future Zamasu (a true immortal) through the Potara earrings, the resulting entity inherited a critical flaw. One half of his body possessed genuine immortality while the other did not. Under the immense stress of battle against Goku and Vegeta, this contradiction manifested physically.

The right side of Fused Zamasu's body began to swell and distort, taking on a purple, almost liquid quality. His right eye changed color, and the overall symmetry of his body was destroyed. Despite his claims of divine perfection, his appearance became increasingly monstrous. This was not merely cosmetic damage; it represented a genuine breakdown in the fusion itself, as two incompatible biological templates fought for dominance within a single form.

What makes the Mutation particularly dangerous is that it actually increased Fused Zamasu's combat power even as it destabilized him mentally. He grew taller, more aggressive, and capable of withstanding attacks that would have overwhelmed his normal fused state. The corrupted mass on his body could regenerate and even expand, giving him additional reach and striking power. Against Vegito Blue, Zamasu powered up further into a truly gigantic version of this form, towering over his opponent.