Complex sentence: Ganthet reveals that this is the White Light Entity that triggered existence and that life actually began on Earth, not Oa, and that the Guardians upheld the lie to protect the Entity and justify their power.
Split into simpler sentences: Ganthet reveals that this is the White Light Entity that triggered existence. He then reveals that life in the universe actually began on Earth, not Oa, and that the Guardians upheld the lie to protect the Entity and justify their power.