Lower down the comments, you will see, it's often confusing how to break open the seal :P
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