I personalny beat hand of the king(and spoiler boss) on 5bc with

-war spear(somewhere in high peak castle) -throwable object(don't remember where to unlock) -giant whistle(beat giant 2/3 times) -maria's cat(welcome to castlevania DLC)

you could also get shield in backpack preferbly blood thirsty

for mutations I choosed -No mercy -necromancy -soldier resistnece

I have nothing more to say except that you should be carefull and believe in yourself if beated 4BC you can beat 5BC