User blog comment:B214/Volume 22 spoilers/@comment-73.160.58.215-20160723140310/@comment-24.113.252.213-20160723211638

The Extra Demons are Clans of Devils that aren't listed among the 72 Pillars (Lucifuge, Belphagor, Aboddon, Mammon). They are clans that mainly served the Original Satans directly, and have decided to not involve themselves in the current government of the Underworld. Anyone who wants to involve themselves would have to leave the clan and break any connections they have to them.

Examples:


 * Grayfia left the Lucifuge Clan to marry Sirzechs.


 * Roygun left the Belphagor Clan to participate in the Rating Game.


 * Bedeze left the Abaddon Clan to participate in the Rating Game.


 * Kuisha left the Abaddon Clan to become Sairaorg's Queen.