I was a bit confused so here's a short guide of sorts for anybody else.
What you are "supposed to do"
1) Find a ruins area with a purple orb and press interact (E) to get an arrow
2) Find a ruins area with a cannon. Interact with a Cannonball to grab one then bring it to the cannon.
3) Interact with the Cannon, aim, and fire at the succubus to knock her down.
4) when the succubus is knocked down draw your crossbow (H), knock your arrow (R), and then aim for the glowing pendent. You'll have to be rather precise
5) As of right now that seems to be all there is to it. You can't defeat the succubus and shooting the pendant has no effect besides making her cry out
Besides that, what she can do to you:
1) While standing she has a right footed stomp and a left footed stomp that ends with her crushing you
2) While standing she has a grab where she will tease and then either crush you in her palm or devour you
3) While crouching she has a grab where she will swallow you quickly
4) While crouching she has a sit down crush attack if you are behind her
5) While damaged and near her left hand she will attempt to crush you with her fist
6) While damaged and slightly in front of her she will attempt to grab you and then either place you on the ground and smash you or chew and then swallow you
7) While damaged and underneath her she will try to crush you with her chest
I think that's all the animations in the game for now. Let me know if I missed any.