Mal Team Force Member 7

Mal is the character that is pretty much Pure Mystery. Unlike all the other characters, Mal is the one that keeps everyone guessing what is going to happen next.

Why Mike is not Mike right now
Mal came back 10 years later with all the personalities. He then vowed revenge on Mike and took over again. Then he set out, and went into Mello's Mafia and got hit in the head with a shovel, bringing Mike back out. The next day Mike went and joined the Team Force, feeling a connection to them somehow. He was assigned to do the cas,e but, when it came to getting fit, Spvetlana came out and told the Team Force her name. After that the team figured it out soon, trying to find the Mafia base. Mello quit the Mafia and re-joined the Team Force, because most of his members died or quit.

Mike then went over to Light one day, hoping to give freedom to his personalities. Instead, Mike got locked up in the subconscious and turned into a personality. Mal came back out and thanked Light. Light was actually paid by Mal to do that someday, and the promise was fulfilled.

Mike only gets out when somebody is in danger, and its because of Light's Magic Dust that it happened.

How Mal First Came To Be (I agree 100% with NovakCat on this one)
I was created by Mike to be a friend to him, and to suffer through the abusive father and all the school bullies Eventually I became Mike's escape from the pain, and all I ever got was the pain... The hurt. I learned from very early on that this is a very dark world, and that I needed to be evil myself in order to survive in it :Mal

Why He Was CHOSEN Out Of All People
Mal caught Ryuzaki's eye with his skills of fighting, his inteligence and his skill of making great plans. Once he joined, L also saw Mal was very cooperative. (pretty much because, in return for Mal joining, Ryuzaki Erased all his police records)