Key Demon

These demons are very old and powerful beings that are typically old and are skeletal looking by Nature. They have been around so long that they've protect the keys to Gates and portals throughout the Universe. The key has become a such a part of them that they cannot release it or it will kill them plus these demons have become called the key Demon in it has infused with their body and become a part of them to where no one can ever get their gate or portal ever again or even try. They're holders of sacred knowledge and forbidden Magic under usually willing to teach the keeper what they know. They also tend to know various other black arts and dark arts Magics.

It's differs some are lonely some want to teach us so they are not forgotten some want to corrupt US with their magic and knowledge. This is usually the reason they want keepers but on rare occasions they require a protege.