When you meet with Geldis Sadri at the Retching Netch in Raven Rock, ask him if he has heard any interesting gossip lately. The bartender will tell you of werewolves who are supposed to be demolishing the area of Frostmoon Crag. The people living in that cave will probably be able to tell you more - head there to speak with them.
The cave can be found halfway between the Abandoned Lodge and the Altar of Thrond - that is southwest of Temple of Miraak. Once you get there, the hunters will immediately ask you to leave their premises. If you hesitate for too long, they will change into werewolves and try to kill you.
The key to victory is defeating the enemies before they can change - it takes a couple second, during which the monsters are completely defenseless. With their transformation over, they will surely cause you more trouble. Luckily there are only four enemies, so you should be alright.
Notice! If you're a werewolf yourself, they will greet you honorably and peacefully. You can even trade with them - they have some useful artifacts.