Thomas

He's actually a scarecrow, brought to life with black magic.

He is an ex-serial killer.

I think I'm going to put him in a story callled 'The Eccentrics'. 

He travels with Nina and her little sister Rosa, two girls from Old Mexico who have extraordinary powers. 

His job is to protect them from any harm.

He accepted the job, as it replaces his prison time. Since Thomas himself contains a great deal of dark matter inside of him, the head-honcho at the prison, a person everyone refers to as 'The Governor', said that he was a special case who had something in common with the girls, therefore he was chosen for the job.