Chiltara

Chiltara, The Vile Frost Stalker, is a randomly spawned Unique female Wintersbane Huntress in the Caverns of Frost in Act III of Diablo III which are located in the Fields of Slaughter.

She is best known for dropping the Gibbering Gemstone, which is required to craft the Staff of Herding and gain access to Whimsyshire.

She only spawns in level 2 of Caverns of Frost which are not guaranteed to spawn. Chiltara herself is also not guaranteed to spawn, and does not guarantee a drop of the Gibbering Gemstone.

As of patch 2.4.1 it appears that she spawns a large percentage of time, but getting the gemstone to drop has a very low percentage. She usually appears right at the end of the cave, be it by the Resplendent Chest, the Teleporting Stone or in a dead end tunnel.

In combat, she has Orbiter and Frozen affixes.

Before patch 2.0.6, in addition to the gemstone, she also had a chance to drop either a Frozen Blood or Urn of Quickening.