Metamorphose

Metamorphose (肉体変化 (メタモルフォーゼ) ), also known as Metamorphosis in the Baka-Tsuki translations, is an esper ability that is purported to exist in Academy City. As it name states, it is a power that allows the user to change their appearance.

Principles
According to Etzali, the ability allows someone to have a face or body similar to others, though it is apparently impossible to change in a genetic level. It is probably similar to Aztec's magic, which uses the flaying of skin to use a disguise.

Tsukuyomi Komoe references that said ability is rare, and that only three espers in the whole of Academy City have that ability.