Gleeok Guts are a material found in Tears of the Kingdom.
Tears of the Kingdom
"A rare and precious, albeit creepy, material that pulses even after its former owner has been vanquished. Cook it with a critter to make a powerful elixir."
Gleeok Guts are dropped rarely by Flame Gleeoks, Frost Gleeoks, and Thunder Gleeoks, and almost always by King Gleeoks in Tears of the Kingdom. They make blunt weapons when fused, but with a fuse attack power of 1 - combined with the high price and difficulty of obtaining - they are wasted doing so. They can be sold to merchants and shops for 200 rupees a piece, or used for black dye at the Kochi Dye Shop.
Gleeok Guts can also be cooked with Bugs, Frogs, or Lizards to create Elixirs, where they contribute an above-average +02:40 to the duration of a timed effect, and a 30% chance of a critical success when cooking an elixir.
Eighteen Gleeok Guts are required for armor upgrades. Nine are required to upgrade the Royal Guard Set to ★★★★ (three apiece for Royal Guard Cap, Royal Guard Uniform and Royal Guard Boots); and nine more to upgrade the Ancient Hero's Aspect to ★★★★ .