The incorrectly spelled word is serpant. The correct spelling is serpent. It is a long, legless reptile with a long, thin body and often with a forked tongue.
Servant is spelled correctly. It is a person who works for another person, typically in a domestic capacity.
Service is spelled correctly. It is the act of providing help or assistance to someone.
Session is spelled correctly. It is a meeting or period of time for a particular activity.