- "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
Ancient Cores are a type of item in The Legend of Zelda: Breath of the Wild. They are a Guardian Part type rarely obtained by defeating walking or flying Guardians. Sentries, level III, and level IV Guardian Scouts drop Ancient Cores as their rarest drop while Guardian Stalkers, Guardian Skywatchers, and Guardian Turrets all drop Ancient Cores as their second rarest after Giant Ancient Cores. They can also be found inside certain Treasure Chests inside certain Shrines. Rarely one may drop when Link lifts broken guardians (with out legs) in bodies of water (or certain areas that fill up with rain water during rain or thunderstorms storms) with the Cryonis Rune, however 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.
Ancient Power Source
Like Blue Flame and Giant Ancient Cores, Ancient Cores are a type of ancient power source. They are power crystals created using lost ancient Sheikah technology which were used as power sources for ancient machinery such as Guardians thus are invaluable to modern researchers such as Purah and Robbie whom can use them to either upgrade, develop high-tech equipment, or to power certain pieces of technology they develop as while Blue Flame is a free energy source it requires a Furnace thus is not a viable option for technology that is intended to be portable thus Ancient Cores function similar to a battery. It is implied that Blue Flame is unrefined Ancient Energy collected by Ancient Furnaces thus presumably the Ancient Cores contain or produce refined ancient energy. Additionally they apparently act as power sources for weapons such as the Ancient Short Sword, Ancient Spear, and Ancient Bladesaw as they are used in their construction thus presumably the weapons break when their cores run out of energy. The energy produced by these weapons resembles Blue Flame albeit apparently refined into plasma-like energy that can be used to form energy blades or spear points that can cause high damage to Guardians. Ancient Cores are also used to construct the Ancient Helm, Ancient Cuirass, and Ancient Greaves though armor apparently does not use much energy as it never breaks though presumably it is the source of the glowing effect that certain sections of the armor emit. Great Fairies use Ancient Cores for the Ancient Armor set's 3rd tier upgrades. Ancient Cores are also required to obtain an upgrade for the Stasis Rune allowing it to be used on enemies, though it is unclear if Purah uses them to craft the upgrade or simply accepts them as payment for allowing Link to use her Guidance Stone to receive the upgrade as Ancient Cores would be useful to her research as they are a portable power source. However they are smaller than Giant Ancient Cores thus presumably contain less energy and are unsuitable for powering ancient technology such as Guidance Stones that require large amounts of raw energy like Blue Flame. Additionally Shrines require such large amounts of energy that Sheikah Towers are used to power them instead of either Ancient Cores, Giant Ancient Cores, or Blue Flame. However they were apparently cheaper for the ancient Sheikah to manufacturer as Giant Ancient Cores are less common than Ancient Cores. Blue Flame requires massive Ancient Furnaces built upon deposits of ancient energy though the Flame is unstable and vulnerable to going out or being doused by water while Ancient Cores and Giant Ancient Cores safely contain the energy. Some Sheikah Monks also left behind Ancient Cores inside their Shrines as rewards implying they may have been involved with their construction and/or development 10,000 years prior to Breath of the Wild. Tu Ka'loh also apparently left behind both Ancient Cores and Giant Ancient Cores in chests hidden in the maze within the Lomei Labyrinth Island.
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 increasing its offensive capabilities and giving Link a new method for attacking enemies.