Nemosyne

Angels granted the power to erase memories and subsequently, the powers of other angels. It is not so much exactly a 'type' of angel, but a job. Any angel can become a nemosyne, provided that they have the abilities to do so.

They're easily distinguishable by their metallic markings - meant to mimic the natural markings of Lucifer. Metatron is the exception of this, namely because he did not choose to be the leader.