The Energon Pub

Turns out that Guiltor that was on Livedoor a little while ago was by Freestyle (but is freestyle some random dude or just a place to showcase customs?) anyway the site doesn't have the link to it on the main page but I was bored and typed in the next number up from the current custom and BAM next thing you know I dropped my wallet and nobody told me.

Link

and for the benefit of the people who have no clue as to who Guiltor is... click me but not hard. Scans and translations by the good people at TFArchive.

So... He's a combination of Prime's and Megatron's bodies with Starscream's spark? Weird.

Yup. He was built by the Quintessons to defeat Galvatron and Rodimus.

I don't know about what the text on the page says specifically, but the character is from the G1 manga. As someone else said, he was built by the Quintessons to defeat Rodimus but fails. I can't remember, but Galvatron and Rodimus team up to destroy it and Starscream's spark escapes.