Melchior

Melchior is one of the three members of the Grigori: the supreme advisors of the True Cross Order.

Though his appearance is greatly shielded by the hooded ornament that he wears, Melchior appears to be a rather aged male, with a very long silver beard. Beneath the garments, Melchior wears dark robes; from the ornament dangles a light-green veil that is parted, giving one the view of Melchior's mouth, only.

(Source: Ao No Exorcist Wiki)