Ttik was once a paladin; however, the Light was stripped from him when he failed to save the life of his companion. After many years of sorrow and despair, he found comfort in death.
The Lich King, upon finding his lifeless body and sensing the pain in his heart, resurrected him and recruited him to fight for the Scourge. When the Lich King betrayed him, he fled.
Now, he again fights for the Light while choosing to remain in the Dark. The Dark affords him spells and abilities that he would never be able to use if he were a paladin.