Creaking Skull Manipulation

Setup:
1. Suspend the game and reload after getting into the pre-creaking skull room to reset the RNG.
2. After getting back into the pre-creaking skull room, hold right throughout the entire room and kill the 3rd candle (do not do any back dashes)
3. Do the fight like normal and do a back dash towards him after your final harpoon
4. Wait to see what his final action after you backdash; your positioning/timing of everything will usually cause the RNG to be at one of two adjacent values in the prng sequence

Action 1: femur smash
If you see him start to raise his femur to smash it on the ground, kill him immediately(rng will stay the same until the femur hits the ground, so you have plenty of time)
http://puu.sh/nTB7L.mp4

Action 2: Crouch>fireball
If he chooses to crouch down, he will shoot a fireball right after. He makes a certain noise when he does the crouch move; kill him immediately after this noise. If you wait too long he will start to absorb yellow energy particles into his back to shoot a fireball which change the rng
http://puu.sh/nTCMY.mp4

Action 3/4: Fireball/step back
If he does either of these moves something was off wise in the fight. I find that if my positioning and harpoon timing are *mostly* consistent(not exact), he will do one of the first 2 actions almost every time

There might be other RNG setups that involve more back dashes in the previous room, but this is the first one I could find that involved a fight where he didn't actually get a fireball move off(sometimes you will kill the fireball with a harpoon and sometimes you wont, and the fireball advances RNG for every frame it's on screen so you really want to avoid that move altogether).