Dread Masters (Paradox series)

Dread Masters were an Organization within Sōsuke Aizen's Arrancar Army and were ranked with five of the most deadly enemies of Soul Society and their intention to recruit at least eight more, each Dread Master has a Immense Spiritual Energy level on par with the twelve Golden Zodiac Knights within the Royal Guard and Yan Diyu has one even surpassing that, they are powerful combatants that fight without using their Zanpakutō thereby fighting similar to the high ranked members of the Royal Guard: with wit, Spiritual energy (including Hollow-like abilities), Kidō and Hakuda.

Trivia

 * The Dread Masters represent Aizen's equivalent of the combatant Royal family members and the Twelve strongest members of the Soul King's Royal Guard.