- "This crystal was made using lost technology. At one time it was the power source for ancient machines. This item is very valuable to researchers."
- — In-game description
The Ancient Core is an item in The Legend of Zelda: Breath of the Wild. It is a Guardian Part rarely obtained by defeating certain types of Guardians. It can also be found inside certain Treasure Chests inside certain Shrines. Rarely one may drop when Link lifts a broken guardians (with out legs) in bodies of water with the Cryonis Rune, however it should be noted that Guardians Parts obtained in this manner are dropped at random and has nothing to do with the broken Guardian itself or where it is located.
Link can also purchase them on rainy days from the traveling merchant Teli who travels around the Necluda province. Like all Guardian Parts, it is a piece of ancient machinery created by the ancient Sheikah.
Ancient Cores can be used by Great Fairies to upgrade certain armor. At the Akkala Ancient Tech Lab the Ancient Oven Cherry can use them to forge certain types of Ancient Soldier Gear after Link relights its Furnace during "Robbie's Research". Additionally like Monster Parts, Link can use them to create Elixirs by cooking them with Frogs, Lizards, or Bugs.
Related Side Quest
During the Side Quest "Slated for Upgrades", Purah offers to upgrade Link's Stasis Rune if he brings her three Ancient Cores. Once he brings her the necessary materials, she will allow him to use her Guidance Stone to upgrade the Stasis Rune to Stasis Rune+ which allows Link to use Stasis on enemies.