You have no hands and so cannot use weapons, shields or rings as well as the expected armour restrictions. On the plus side you have excellent unarmed combat and you grow an extra head every 3 levels (or whatever) allowing you to wear multiple amulets.
Also multiple hats!
kimchi already has a hydra species; worth looking at what it does (but I’m pretty sure it can’t wear multiple amulets…)
Would it have hydra head chopping mechanic?