I never noticed until recently that every hydra head has a certain affect that is supposed to proc when the head is decapitated. I don't think all of the head effects are procing though. such as I've not noticed recieving a veil but only the true fear removal from torment and I have not seen the 100% tm reduction on all heads from mischief. the others I don't care that much about and havn't bothers to see if they even work or not