Hundreds of thousands of years ago, Rayblood's body was destroyed, spreading his genes throughout the universe and creating the Reionics. Rayblood continued to exist in spirit, however, and began searching for a worthy successor to him.
Ultra Galaxy Mega Monster Battle
Rayblood is mentioned in episode 12, the penultimate episode of the series, by Kate who explains his origin and states that he is the creator of all the Reionics.
Ultra Galaxy Mega Monster Battle: Never Ending Odyssey
In the sequel series, Rayblood is revealed to be sealed within Planet Hammer. After gaining enough power, Rayblood called out to Reimon, luring him into the depths of the planet. Rayblood then summoned Armored Mefilas to fight him to test his abilities.
Rei manages to defeat Mefilas, impressing Rayblood. The ancient entity then reveals himself and offers to make Rei his successor. However, Rei refused, prompting Rayblood to summon and possess Armored Darkness to kill Rei. The Armored Darkness succeeds in defeating Rei's Gomora, but Grande and Red King appear soon afterward, revealing that they followed Rei. Red King EX and Gomora EX then work together to defeat Rayblood and succeed in doing so.
Rayblood later attempts to suck ZAP SPACY into a black hole as they are fleeing the imploding planet. However, Ultraman and Ultraseven use their Specium Ray and Wide Shot to destroy Rayblood's core, allowing ZAP SPACY to escape.
Mega Monster Battle: Ultra Galaxy Legends The Movie
Rayblood appeared to Belial after he was banished from the Land of Light and fused with him, transforming Belial into a Reionics and granting him powerful new abilities.