The most vicious and evil Ultra born from the Land of Light who tried to take over the galaxy.
To seek for greater power, he attempted to harness the power of the Land of Light’s power source: Plasma Spark, and was exiled by this criminal act.
He was then infused with the genes of Alien Rayblood, which corrupted Belial with even further negative emotions and fully drowned him into the dark side. At the same time, he had become a Reionics with an army of hundred monsters.
Belial invaded the Land of Light for revenge, but was defeated by Ultraman King and was imprisoned to the Space Prison. This event was later known as the Revolt of Belial.
Many years later he was freed by Alien Zarab and regained the Giga Battlenizer, as well as his army of more than 100 monsters.
For revenge, he tried to attack the Land of Light once again, but was foiled by Ultraman Zero and ended up falling into magma.

In ULTRAMAN GEED, while healing from the severe damages during the battle against the Inter Galactic Defense Force, Belial plots to fully recover and take over the universe once again by using his servant.
He fights against his son Geed, a clone who was initially made to be used by Belial.
Belial once completely absorbs Geed and strengthens, giving Ultraman Zero who had come to help, a hard time.
However, by regaining his conscious, Geed comes back and destroyed Belial with his special beam, Royal End.
Belial was later revealed to have survived the attack and revives himself with the reclaimed capsule, transforming him into a new ultimate form, Belial Atrocious.
He demonstrates his newfound powers by overwhelming Ultraman Zero and Father of Ultra.
But with Geed’s determination and courage, Belial was finally destroyed for good after Geed attacks and manages to drag Belial into a dimensional void.
In the spiritual world, as Belial responds to Geed’s tears, the grudges of Rayblood dispels from him, transforming him back into his former self Early Style.
Lastly, Belial is shot with Geed’s Wrecking Burst, and his body destroyed in the explosion. Belial’s soul was also locked into a different dimension by his own son.