Alter ego
An alter ego (from Latin, "other I") is another self, a second personality or persona within a person. The term is commonly used in comic books, for the secret identity of a Super Hero and Super Villain.
An alter ego is usually used by Super Heroes to conceal their identities in order to protect their friends and family from harm at the hands of their enemies, whereas supervillians usually
have an alter ego to make sure they don't get arrested.