I want to start talking about the first 'mini' Boss, the guy with the staff.
I saw a 'no death' video on youtube but i dont how it was done, if it was TAS or not but i think its maybe possible it we identify some patterns.
Usually it appears that the best strategy is to jump dive kick him and then hit him when he try to get up, run and try again. Sometimes after he falls, he immediately crouch and defend, and if you hit in that time you will get hit back, but sometimes he defend the first hit and the following sword hit can hit him, still dont know if its random. Sometimes i use the jump sword attack after he does the kick attack and it hit, but sometimes it gets defended and he does another kick instantly and you get hit, also dont know if random or the hit window for you is realy percise. i also noted that after like 1 third of his heath it gone, he gets more agressive (and defensive), and in the last third of his life he can get hit more often, im still not sure about that or im imagining things. I also imagined using the ranged attack that const life to get him down from far away then hitting him when he gets up in crucial points like in the end of his life, but im not sure its worth the risk.
The Tree Boss also has a video of someone killing it with no hits(same youtube video), he defends alot and seem to know the patterns, but i cant understand how the tree didnt grab the guy atleast 1 time as block dont work for that attack. The best strategy i found is to just constantly dive kick and cast spell(3 possible) on it till it dies, but havent dug deeper to see if its the fastest way, but if i aim for a no death, i need to find better strategy .
the rest of the stage its just strategy to kill mobs using the ranged attack that cost life in certain parts, still open for optimization were and when, also i think luring the guys that drop spells and food closer to you for fast grabing it and continuing foward is possible. The first 2 mobs and the 2 after at the start of the stage can be killed with 3 hits hitting both at same time, i think knowing were mobs spawns can be used way more often than i saw in the speedruns .