Looking forward to seeing the CS then. For now though I can provide some more details about my idea.
Basically the planet-sized organism was not originally that, but evolved at some point on this world, and eventually grew to take over the planet entirely. It has the ability to assimilate, adapt, and absorb biological matter, and so over hundreds of years it consumed and replaced every other living thing on its planet, creating a planet-sized meatball with a planet-sized consciousness.
Naturally from there it grew curious about other worlds and expressions of life, and has created mentally-linked ambulatory offspring/offshoots of itself to explore the cosmos and proselytize how great it is to be a meat monster. My Champion would be a special form of one of these missionary puppets, fully independent and with a realized ego, which gives it unique properties compared to the rest of its "species."