Mugen Kagemaru is the main antagonist of the ARG, Mugen does not have sense of humor on his own, He is currently using the body of Gabe Newell as his host.
Mugen's true origin has yet to be confirmed. The earliest documented information about Mugen is the post on WH that says "Let's get this thread to 1 million" on Aug 31 2012
Before the Internet Detectives was created, Gaben was visited by an entity called Lona. Lona copulated with Gaben, creating an evil thought to be the Tenebros Lonk. After Tenebros was created, Lona bestowed Gaben with a great deal of knowledge. Gaben would eventually become a vessel for the True Father. Since the True Father requires a vessel, it is likely that the True Father is actually Mugen Kagemaru.
Mugen doesn't belive your identity, reports have reported that he tried to kill the postman yelling "Fucking Jos get out of my house".