he can read people's minds.
the first mind he dove into was his fathers. Mantis saw his fathers hatred and burned down his village.
after reading too many sick minds of murderers he became insane too.
during Liquid's revolution he had the idea of disgusing Decoy Octopus as the DARPA Chief.
After his death, he feels guilty and helps Snake.
It was the first time he used his powers to help someone. He found it nice...