Complex sentence: It is later revealed that MECH was actually started by Quintessons, the Transformers' "creators" disguised as humans and that the Quintessons have had a history on Earth and several other planets in the galaxy.
Split into simpler sentences: It is later revealed that MECH was actually started by Quintessons, the Transformers' "creators" disguised as humans. The Quintessons have had a history on Earth and several other planets in the galaxy.