The Darkness Knights (暗黒騎士Ankoku Kishi) is a group of Guardian that serves under Gambiel.
Z/X Encyclopedia Entry
Putting on the Masks of the Divine Progenitor of Envy, the Angel turned Diabolus Gambiel obtained a new power, "Reversal". It awakens the sleeping emotions in the subconsciousness of person who comes in contact with this ability, which is usually negative emotions... and turns their character and way of thinking into the complete opposite. This is especially useful on the Guardian who held firm belief to protect the White World, and she make use of this ability to form a private army.
