Snakfrum has multiple spawn points I marked the ones I know about on the map. He roams around in side the fort with all the summoners, he also roams around the ghost area, and the little island and lake. Snakfrum puts a totem down that drains your power and slows you. I Always burn the totem down then kill him. He also tries to heal himself, you will see the green induction ring under him when he is trying. Just stun him fear him or kill him before he gets it off.