Potter, Colan and McLeod bring Jemm, Son of Saturn to an end with issue 12 (Aug 85).
So of course this is a big fight finale. The Koolar holding Luther has the ability to enter and animate objects, which ups the scale for the battle, and gives Colan a chance to have fun with the art.
But the tale feels like a downer. Jemm more or less forcibly brings peace between the red and white Saturnians. The prophecy had him fight to protect them all, and it turned out that he needed to protect them from Tull, but Jemm's actions won him no friends on either side.
Still, Jemm does the right thing. He defeats the white Saturnian and frees Luther.
There is some very strange stuff with Bouncer and the homeless people. Bouncer and Luther's older brother have become friends since spending time on the streets, and working together against Tull. But the homeless people reject an offer to provide them with shelter, because they love living on the streets. Yeah, right.
So Luther winds up back with his brother, who is no longer a gangster, and Bouncer, who also has changed his ways. Jemm flies off as the boy cries about how much he cares for Jemm.
I am honestly not surprised that this didn't spawn any continuation. Jemm is too much like the Martian Manhunter, and the story could have been better told. Jemm does return occasionally over the years, and made an appearance shortly after this series ended, on the Monitor's satellite in Crisis on Infinite Earths.