Defeating Pale Prince, a modded version of Pure Vessel created by 56. This mod boosts Pure Vessel making him faster, gain new attacks, and overall makes him slightly more difficult.
This one's pretty rough and the hardest modded boss I've beaten. It's really easy to make mistakes on this fight and with 3000 health it takes a lot to finish Pale Prince. The first phase isn't too bad and mostly slows you down. Fire trails with the lunge/triple slash make dashing through Pale Prince a bad idea (unless you dash right where he starts the attack). It's when you hit phase two that things get interesting. Fake out dashes (which sometimes work in your favor if PP switches to a triple slash) make it safer to just not try to pogo lunges. Both void streams have their problems in anticipating them. Then in P3 you get the javelin maze, which isn't too difficult to perform the small hops to get through it but by that point playing it safe with descending dark is so much easier.
I found myself liking Lifeblood Core for the ability to take two extra hits (very handy when learning the fight). However, using Quick Slash or Shaman Stone likely would have sped up the fight a good bit. There are especially more openings to really make use of Quick Slash.
Dashing against the wall at the start wasn't some grand strategy - my cat simply wanted attention during the boss scream and when I went back to play my fingers were on the wrong buttons. But it all worked out in the end.
My thanks as well to TheDarkMarioAndSonic for reminding me of the most important aspect of this mod: No matter how buffed Pure Vessel might be, this is only a fraction of his true might if he still had his cape. #MakePureVesselCapedAgain
If you're wanting to try this, it can be installed through the mod installer on the HK Discord modding channel in pinned messages.
The HK Discord link is https://discordapp.com/invite/hollowknight
Or you can get the modinstaller directly from https://radiance.host/mods/ModInstaller.exe