The following section contains information from a previous version of StarCraft II: Heart of the Swarm which is no longer valid.
Yeti (a.k.a. snow beasts) were fauna which live on Kaldir, a protoss-settled ice world in the Koprulu Sector. A large number of them reside in the Ice Valleys. They are led by yeti matriarchs.
Yeti appeared as a third force in the development build of the Heart of the Swarm mission Harvest of Screams (at the time named Silence Their Cries}}. They attacked both the zerg and protoss forces at will. Unlike the matriarchs, they did not present much of a threat. These were changed to ursadons in the launch build of the game.
Heroes of the StormEdit
In an older development build of Heroes of the Storm, defeating a yeti camp gave runestone rewards, which a hero could use to summon yeti minions, potentially ten or more, at allied towers. These were changed to mercenary camps in the final release.
The Yeti is an ape-like mythological creature, said to inhabit the Himalayan region of Nepal, India and Tibet.