On the one hand, this suggestion seems like a simple addition: recoloring the existing bear model with a near-white coat.
On the other hand, though, I’m suggesting something a little more: Polar bears are the only creature known to actively stalk and hunt human beings.
Most creature and NPC enemies in the game have a distance in which they will stop pursuing. What I’m suggesting is for Polar Bears to be added, not only recoloring an existing model (so only minimal art assets would be needed), but more importantly, giving them a ‘non-distance’ pursuit behavior. Let a Polar Bear track, stalk, and hunt down an exile relentlessly. Furthermore, make them more dangerous than normal bears. Its known that real Polar Bears can kill with a single swipe of their paws. So give them ‘one-shot’ or near ‘one-shot’ capabilities.
Oh, and Polar Bears are also very good swimmers, too.