Molduga Jaw is a material found in Tears of the Kingdom.
Tears of the Kingdom
"A hard jawbone. Its shape allows a Molduga some maneuverability in the sand. Attach it to a weapon to greatly increase its attack power. Cook it with a critter to make an elixir.""
Molduga Jaws are dropped by Moldugas on defeat. They have a fuse attack power of 32, and make blunt weapons when fused. As a bone item, Molduga Jaw Fused Weapons synergise with the Bone Attack Up Set Bonus of the Radiant Set, meaning they gain an 80% boost to attack power when the set bonus is active. Consequently, it becomes the single most powerful reusable fuse item in the game with Bone Attack Up active (Gibdo Bones are more powerful, but also are single-use), beating out even the Silver Lynel Saber Horn.
They can also be used in cooking elixirs, which increment Link's stats for a period of time. They contribute a slightly-above average 1:20 to any duration the elixir imparts, as well as boosting the critical success chance by 10%.
Nine Molduga Jaws are required as part of the cost of upgrading the Radiant Set to ★★★★ level, three each for a Radiant Mask, a Radiant Shirt and pair of Radiant Tights. They are not used in any other armor upgrades.
They are not required as part of any quests. They can be sold to merchants and shops for 30 rupees a piece, or used for brown dye at the Kochi Dye Shop.
Default Tears of the Kingdom Hyrule Compendium picture