From Diablo Wiki
Chiltara is a Unique (purple) Lacuni huntress who only appears in the Caverns of Frost dungeon below the Fields of Slaughter in Act III. Chiltara is a much-farmed enemy as the only source for two different legendary materials, and may drop a third as well.
Chiltara follows a freezing theme, and has the Frozen Elite Affix, which creates small ice grenades that explode after a second, dealing a freezing effect to anything in their blast radius. She is also highly resistant to cold-based attacks.
- The Gibbering Gemstone, one of the materials required to craft the Staff of Herding, which is required to enter the Whimsyshire secret level. (Only one of these is required for the staff, per account.)
- Frozen Blood, a legendary material required to create Utar's Roar, a crafted legendary one-handed axe. (One of these is required for each craft of the Axe, which may require multiple rolls to spawn at the desired quality.)
- Urn of Quickening, a legendary material required to craft the Kethryes' Splint legendary bracers. This material may be dropped by any Unique Lacuni huntress, including Chiltara.
Chiltara is a very rare spawn and may require many farming runs to find and to secure the desired legendary material from. Thankfully, the drop rates for legendary materials are calculated independently, as sort of an "add on" drops, rather than either/or items that would compete for drop priority. 
Chiltara is associated with the following achievement:
|Monsters of Diablo III Beasts Beasts: Superunique Demons Demons: Superunique Humans Humans: Superunique Undead Undead: Superunique Objects Bosses Boss Mods Monster Info Fanmade|
Bat - Beast - Blood Hawk - Demonic Hellflyer - Electric Eel - Khazra - Lacuni - Lamprey - Quill Fiend - Rockworm - Sand Monster - Sand Shark - Sand Wasp - Scavenger - Spider - Spiderling - Swarm - Withermoth - Wood Wraith -
|Primary Quest Uniques||
Act One Bosses:
Skeleton King -
The Warden -
Strong CC (Limit 1): Knockback -- Nightmarish -- Vortex -- Jailer
|Act One Uniques||Araneae - Web Spit||Leoric - Summon Skeleton, Teleport Strike, Triple Cleave||The Butcher - Smash, Grappling Hook, Spear, Frenzy Charge|
|Act Two Uniques||Maghda - Forcefield, Summoning Ritual, Punish, Moth Dust, Teleport.||Zoltan Kulle - Fiery Boulder, Time Bubble, Ceiling Collapse, Energy Twister,Vanish, Creepy Laugh||Belial - Phase One: Triple Fireball, Summon Vipers. Phase Two: Poison Meteors, Ground Pound, Lightning Strike, Lightning Breath.|
|Act Three Uniques||Ghom - Acid Slime, Sneeze, Gas Cloud, Chomp.||Siegebreaker - Triple Hit, Charge, Leg Stomp, Grab and Throw.||Cydaea - Pain Bolts, Web Trap, Spider Pits.||Azmodan - Bellyflop, Laser Attack, Falling Corpses, Demon Gate, Pool of Destruction, Globe of Annihilation.|
|Act Four Uniques||Rakanoth - Cleave, Teleport Strike, Blade Strike, Volley, Summon Minion.||Izual - Frost Nova, Frozen, Summon Minions.|| Diablo - Phase One: Claw Rip, Charge, Hell Spikes, Shadow Vanish Grab, Curse of Destruction, Ring of Fire, Ground Stomp, Curse of Anguish, Curse of Hatred. |
Phase Two: Shadow Clone. Phase Three: Overdrive, Lightning Breath.