There's a spirit in there which you can get possessed, cosmetics and effects to not be affected by the fox thingy. You just have to use really strong attacks like 3 dmg then 2 dmg and I think a talisman as well? Anyway yeah.
it has to be specifically a heavy attack (the ones with the little
orange icon and that take 2 turns) and a physical attack (so not a
hypnosis attack or one of the fox attacks), and you have to hit
specifically the tile in the middle, one above the ground
I've found that it works with axe, pickaxe, drill (from lamia corruption), and warpath (from werewolf corruption)
side note: no clue what Greenstar is talking about with the damage and the talisman
I really don't get what's so confusing about it? you can literally just start a new run, immediately bee-line to the shrine, not getting any corruptions, items, or extra attacks, and then hit it with the 'axe' skill you have by default and that works just fine, and from everything I've seen, all heavy attacks (which can also destroy the mini shrines that spawn with the fox girls, and prevent them from spawning spirits when broken) also work, so I really don't get what's so confusing about it