Bubbul Gems are a newly introduced collectible in The Legend of Zelda: Tears of the Kingdom obtained exclusively from Bubbulfrogs—mystical creatures found in the caves and tunnels of Hyrule. These gems serve as currency in trading with Koltin, the brother of Kilton from Breath of the Wild, offering access to unique items, including the highly sought-after Mystic Clothing armor set.
Before they can trade Bubbul Gems with Koltin, players need to embark on a short side adventure. Once unlocked, Koltin can be consistently found at any of these four specific locations. This guide will outline how to unlock Koltin’s shop and where to find Koltin in The Legend of Zelda: Tears of the Kingdom.
How to Unlock Koltin in Tears of the Kingdom (Koltin's Location #1)
The initial encounter with Koltin takes place near Woodland Stable at the southwestern corner of Eldin Canyon. Head northeast of the stable to find Koltin's brother, Kilton, near the mouth of a cave by the small Pico Pond at coordinates 1208, 1214, 0020. Kilton is standing outside the cave entrance next to an oversized 
Balloon cart, reminiscent of his shop from Breath of the Wild.
After the player has spoken with Kilton, his brother Koltin will come running out from Pico Pond Cave. Koltin explains that he wants to transform into the beautiful Satori, the magnificent Lord of the Mountain. This starts the quest “The Hunt for Bubbul Gems!”
Head into the cave and defeat the Bubbulfrog, a glowing frog creature. Collect the Bubbul Gem it drops and return to Koltin. He will excitedly consume the Bubbul Gem, and when he learns that it is not enough to transform him, he will quickly run off. Kilton will let players know that he plans on relocating, and they can find him in Tarrey Town.
Upon completing “The Hunt for Bubbul Gems!” Koltin is unlocked as a merchant and can be found at any of the following locations after 9:00 PM. The player can travel to any of these locations, and Koltin will always be there, as long as it is night. He will accept Bubbul Gems from the player in exchange for monster parts and the exclusive Mystic Armor set.
Koltin Location #2 - North of Tarrey Town
After Kilton relocates to Tarrey Town, situated on the central island of Lake Akkala, players can speak with him to learn about Koltin's current whereabouts. Kilton can be found at the northernmost part of Tarrey Town at coordinates 3961, 1642, 0128.
Kilton will provide directions to Koltin's shop. Koltin’s glowing balloon cart is visible on a nearby hill at coordinates 3662, 2064, 0168.
Koltin Location #3 - South of Lookout Landing
Koltin can also be found south of Lookout Landing on the eastern side of the Passeri Greenbelt at coordinates -0319, -0162, 0022. Simply travel to the Lookout Landing Skyview Tower and head out of the village toward his balloon cart, which is visible from the gates of the town.
Koltin Location #4 - South of Popla Foothills Skyview Tower
To find Koltin at this location, the player can take the Popla Foothills Skyview Tower and head south. Koltin's cart is visible on a hill ahead at coordinates 0588, -2681, 0112. Continue through Farosh Hills, passing a large armored compound full of enemies, until players reach Koltin at the top of the hill.
Koltin Location #5 - South Tabantha Snowfield
The player can encounter Koltin at coordinates -1533, 2386, 0245 on a cliff at the eastern edge of the South Tabantha Snowfield, southeast of the Snowfield Stable and Orochium Shrine. The cliff overlooks the Tanagar Canyon and Koltin and his cart can be found just north of the "Forgotten Temple" text on the world map.
The Legend of Zelda: Tears of the Kingdom is available for the Nintendo Switch.