Erelim is a powerful angel. There's a reason he's the leader of all the other angels. It is a well-known fact not to bother him or do anything deemed impure. They would never think he had any type of secret let alone a dark one.

In the depths of his home there lays a seal, and on that seal lies a demon. A demon that radiates beauty and power, and though the blind archangel can not see her, he knows how alluring she truly is. Which is why he's kept her imprisoned and kept her all to himself.