Wandering Wight and Apramana Bat are the 2 best spirits in the game for meAlso, Wandering Wight is your homie, keep him equipped because that Bonks Adventure to the dome will stagger the fukk out of most bosses especially when they're Immobilized.
Peep game...
Shadow Clones, wait for them to Immobilize the boss, wallop that motherfukker with a full focus attack, when the boss comes out of the Immobilize that your shadow clones hit, now you Immobilize, hit em with that Wandering Wight
That whole sequence right there will take most bosses down to half in the first go