He appears to be a Lord and a Fanatic one at that. It would appear that Adolf is his Childe and that he isn’t to happy with him or that he just set standards too high, damn Lords.
He appears to have knowledge of Theban rituals to some extent, we should research this further if we are to fight him at any moment.
He appears to be short tempered.
He appears to be a member of Lancea Sanctum, we have no real information about his status in the city or in the Sanctum. Adolf notwithstanding Lestat and Luis have stolen the ceremonial equipment he was after and gave it to a mysterious Shadow.
We should tread carefully around Marcus in the future. He is certainly not happy with the outcome.