You can remix this boss add attacks, phases, new songs, new gimmicks. Just don't have you're super strong OC overtake the boss and become it's whole own thing. That's lame. You can update the bosses sprite if you'd like, but I'd prefer if it was recognizable as the same boss from the start. Bassically, don't replace the entire project. After the boss is pretty cool, I'll make a video fighting it and give credit to everyone who remixed in the description.
This is my part, which includes one new attack and a new gimmick: -The new attack is summoning a staff that shoots laser beams. The new gimmick is that, every time the boss loses more health, it has a chance of summoning minions ( based off the Sphere Doomers from Kirby ). The more health it loses, the more Doomers spawn at once. Thanks to @antonio_projectz for the prevoius remix and @jomamajojo for the original project.