Forums → Game Walkthroughs → monster slayer how do you get all the hats?

Start doing the pvp. Each time you face and defeat a team with a hat in use that you don't have you then get that hat.

You get several from the campaign and defeating the final boss. The multiplayer also has many you can get.

On Kongregate, at least, the creator made specific PvP teams that if you fight it awards you with one of the hats the Enemy player wears.