Since ULF is gonna be probably the strongest non admin stand/spec in the game it should be the hardest to get.
This is how I think it should be obtained and the boss specs. So firstly You have to kill dio and go to the volcano there will be a special rock that has the three pillar men engraved onto them where you can put the stone mask and then it will start a countdown for kars to spawn (around 10 mins). Kars will have two forms one being regular kars (same moves as kars with 750 hp) and the other being the ULF (1750 hp and moves TBD). If you kill kars it’s a 100% chance to get the pillarmen mask (use it on Santana to get wamuu) and to get ULF u will need Aja stone which is a 1/5 drop from kars and talk to Tom who will fuse the stone and the pillar men mask for 4K. Also there is a secret ending if kars is killed by a Joseph Hamon it will do the cutscene of kars going to space (to get Joseph Hamon it’s a 1/5 drop from a frog consuming it standless, if you Have Joseph’s Hamon and use an arrow it will become hermit purple -still considered Joseph’s Hamon-)