Djinn are powerful magical beings that slumber within the dungeons that the Magi raised across the land. If someone makes their way to the inner chamber, the djinn may pronounce them worthy and bind themselves to them. They grant great power to those who bear their vessels and to their most loyal followers as well. My king has conquered seven dungeons, so I have seen many djinn. I should be able to recognize one by now and you're nothing like any I've seen.

[It's the short version, certainly, but he's not a magician or a dungeon conqueror himself, so many of the technicalities escape him. He just knows what he's seen at Sin's side.]