Might also want to look into Magic Wall.. as it block enemy projectiles, deals damage to enemies and you can place 50 of them anywhere on your screen before running out of mana. https://imgur.com/NkLLPpX
Edit: Will also add that this made it possible to kill knight boss without moving because of the zoomed out room. Lantern boss got easier as well, since you could leave the walls on his lanterns.. killing them instantly as they came back to life.
Edit 2: It gets a bit crazy when you combine it with potion use and equipment boosting stats.. https://imgur.com/fciiZLu