Spoiler warning: Plot or ending details follow.

"The little twin steps over the little river. My cave rests above that river's source."
— Misko, the Great Bandit

Misko is a character from The Legend of Zelda: Breath of the Wild. Misko is not met by Link but mentioned during the side quests "Misko, the Great Bandit" by the treasure hunters Domidak and Prissen at the Dueling Peaks Stable. Both are searching for one of Misko's treasure cache. He was a great bandit who once lived in the land of Hyrule and was probably from Kakariko Village in the West Necluda region of Hyrule. He is known to have successfully broken into Hyrule Castle to steal priceless relics in the past.

Misko's Treasures

"I hide the eight priceless relics I stole from Hyrule Castle in treasure chests... I shall write down their locations."
Misko's EX Journal

Upon installation of the DLC Pack "The Master Trials", a new mission entitled "Misko's Treasures" is unlocked. Misko is revealed to be a great thief who stole eight ancient treasures from the Hyrule Castle and hide them around the world. He wrote a journal about the locations of these items and left it at the Outpost Ruins. They include the Majora's Mask, the Midna's Helmet, the Phantom Helmet, Armor and Greaves set, and the Tingle's Hood, Shirt and Tingle's Tights outfit. Link can look for them during a series of four side quests.

Side quests

Spoiler warning: Spoilers end here.