Every thief abides by a set of rules these rules are what differs the pros from the ametuers. Crimson Star is part of a family of thieves that have been in Equestria for centuries and he was the leader of a failed but great hiest before disappearing.

"Who am i?", " What's my purpose?" these are the things that Crimson asks himself in the new world inhabited by ponies the only things he remembers is his name and the fact is that he's not supposed to be in that world.