Both have similar functions, which should I use for mech boss fights? I am using worm scarf already
I'm on master mode, what goes in the last one? Shield of cthulhu?Assuming you're on Expert mode and have 6 slots.
I'd go for this, in order of priority:
-Brain of Confusion
-Worm Scarf (you managed to get both? nice)
I do not use the Charm of Myths myself, and rather prefer the knockback immumity over it.