Yan Diyu (Rebirth)

Yan Diyu was the terrifying and prophesied Extradimensional entity that takes on the form and powers of both an Arrancar and a Shinigami, he was said to be the entity that would one day rip down the Spirit King from his throne and destroy the modern world in which he would create his own, many of his followers (including Sōsuke Aizen and Vandenreich) are said to believe that once he replaces the Spirit King he would remake the worlds into a Golden Age unlike any seen before however those loyal to the Spirit King fear the death and destruction to reach that end.

Early existence
Yan's birth was at some point foretold in a Prophecy shortly after the current Soul King took his place on the Spirit Throne,

Personality and traits
Yan was originally a kind and timid youth who came to believe that everyone had a good side, however after awakening his powers during his time in the shadow of the Royal Palace, he became distant and withdrawn.

Yan came to believe that Death is Salvation and believes that by killing someone he is saving them from the pain of life, that death is peace, and that he desires to give everyone who suffers in life.

After finally fully awakening his powers and personality via his first resurrección, Alma Oscura, Yan becomes more cruel and destructive where he believes that death is also a Judgement for those whom destroy the worlds

Physical Appearance
Yan originally had long blond hair that moved out in long strands, after awakening his powers however his golden hair became dyed black due to the infusion of immense spiritual pressure that became the source of his power, he has pure blue eyes and a lithe figure that isn't made of so much muscle rather than superior height.

Yan wears long black robes and sandals on his feet, around his neck is a star-shaped pendant, this Pendant is actually the dormant state of his resurrección forms which suppresses his personality and power and contains his Underworld God Armour which generates out from the Pendant and appears on his body when he enters his second resurrección: La Hampa Dios Blindaje.

Trivia

 * Yan is the name of the Chinese God of the Underworld, Diyu meanwhile is the name of the Chinese Underworld.