Dee is a mutant with the ability to create a miniature duplicate of anyone he comes into physical contact with. Once he has created a duplicate of that person he can force that said person to do whatever Dee wants which includes killing the said person. Johnny also has several tentacles and razor sharp teeth protruding from his chest.
One of the few mutants to remain powered after the House of M incident, Johnny took refuge on the grounds of the Xavier Mansion with other mutants. There he toyed with several people and mutants and eventually killed both Jazz and Mister M.
His current whereabouts are unknown.