I think I cooked (Yes, this was inspired by Griefing from Crimson Chronicles)
Imma do a lore drop here since the only lore for him I have ever posted on Scratch is pretty outdated. Pre-AAA: He was a lab experiment made solely to test the capabilities of a regular object. He was tortured for 5 years in these experiments, and desired nothing but revenge for the ones who made and experimented on him. So one day he broke out of the area he was tested in and consumed the entire supply of a substance the lab was planning to harness the power from, he used his destructivity to wipe out everyone who was there in the lab. He now lives a decently normal life after all of that though. AAA - He was taken into this realm by ???, Starfish Painting didn't want to be there, but ??? drove him to insanity using visions of his past, and Starfish Painting now kills survivors almost remorselessly and willingly, almost, almost is the key word there...