Allen's teacher, a scientist, and also one of the five Exorcist Generals. At the start of the story, he had gone on a journey and stopped corresponding with HQ for four years. Allen fears him, which is hinted from the fact most of his flashbacks that connect to his teacher end with some kind of traumatizing (usually humorous for readers) experience. He also has a habit of going into debt and making Allen work it off for him. It is revealed by Bookman that Cross has the unique ability to convert Akuma, making them to work under his orders. The method of conversion is unknown though. Beside that, it's believed that Marian has the ability to control the Noah's Ark (an ability granted to him by a traitor of the Noah family, who was subsequently killed by the Earl), although it's unknown if this hypothesis of the Earl will turn out to be correct. Marian seems to be the only person the Earl is seriously worried about.
Marian is the only exorcist with two Anti-Akuma weapons. His first one is "Grave of Maria" which is a woman corpse that has a parasite type Anti-Akuma weapon, she only serves Master Cross. The second one is "Judgement" which is a giant revolver gun and Cross's own Anti-Akuma Weapon. Right now Cross is missing after he talked with Allen about his relation with the 14th.
