The Robe of the Tundra is a trophy from a Tundra Mattekar, a new Mattekar introduced in the Keep Your Enemies Closer event. The approximate drop rate for the robe is about one in four. Tundra Mattekars can be found in the mountainous regions of Dereth. Like all the new boss creatures, they can be scarce and difficult to find. When you find a Tundra Mattekar, it will usually be accompanied by a few Dire Mattekars.