An Alien from Nebula M78, where all beings seek to keep peace in the Universe and supervise the right development of life forms on all planets.
Great makes a promise with Jack Shindo to borrow his body, so in human form Jack operates of his own free will, and he uses the Delta Plasma pendant to transform into Ultraman Great. In battle, he uses physical techniques like punches and kicks to defeat enemies, as well as a diverse range of light beam attacks like the Burning Plasma and Knuckle Shooter.
Entrusted with the mission to defeat the Evil Life Form Gudis, he travels to the solar system where they fight on Mars. Jack is caught up in their battle and unable to return home and so Great fuses with him. On returning to Earth, he works with Jack and the UMA to defeat monsters infected with Gudis cells.
Even then he stays on Earth to protect humanity from many monster attacks, but Kilazee and Kodalar appear to eradicate humanity for polluting the Earth. In the grueling battle to defeat them he separates from Jack and flies off with his enemy into space.