Kilton is a Hylian who is fascinated by monsters and has dedicated his life to studying them. Though his research he was able to create Monster Extract which can be used to create various unique food dishes. He eventually sets up a shop called the Fang and Bone in Skull Lake of the Deep Akkala region where Link first encounters him.
Kilton explains that he has been researching monsters and explains that he deals in Monster Parts and will purchase Monster Parts from Link in exchange for the Fang and Bone's special currency called "mon" (represented by a skull icon) which Link can use to purchase various items from Kilton, such as Monster Extract, Spring-Loaded Hammer, various monster Masks which allow Link to temporarily blend in with certain monsters, the Monster Bridle and Monster Saddle for his horse, and an Armor set based on Dark Link.
After encountering Kilton in Skull Lake, Kilton will use his hot-air balloon to tour the land of Hyrule and the Fang and Bone will appear on the outskirts of all major villages at night from 8:00 p.m. to 4:00 a.m.
Additionally Kilton plays a key role in the side quest "A Shady Customer", in which a soldier named Hoz who defends East Akkala Stable asks Link to investigate Kilton as he considers him to be a shady character, when in reality Kilton is just an eccentric monster researcher. Using the Camera Rune, Link can must take Kilton's picture and show it to Hoz, receiving a Silver Rupee as a reward.
Kilton is apparently known to certain people in Hyrule as Chabi, one of the travelers Link can rescue from monsters while traveling throughout Hyrule, has been searching for Kilton's shop, though she is unable to find him at Skull Lake. After he sets up shop, she still has trouble finding him due to him moving around and does not know about the signs or his shop appearing at night. Interestingly, despite this Chabi has managed to obtain Monster Extract, which she gives to Link as reward every time he rescues her from Bokoblins.
Fang and Bone
After encountering Kilton in Skull Lake, Kilton will use his hot-air balloon to tour the land of Hyrule and the Fang and Bone will appear on the outskirts of all major villages at night from 8:00 p.m. to 4:00 a.m. A Sign will mark the locations where Kilton's balloon appears at night after meeting Kilton at Skull Lake. During the day, Link can create a Campfire to past time or if Kilton's sign close enough to town, Link can sleep at an Inn. At night near his shop, sinister music will play which acts as a audio cue that it is nearby. If Link talks to Kilton after sunrise, he will close up shop and disappear.
Kilton's Medals of Honor
After completing the main story and defeating Ganon, if Link talks to Kilton it will lead to three conversations in which will ask Link to defeat every single specimen of three different Mini-bosses in Hyrule as well as any of their variants. These mini-bosses are Hinox, Talus, and Molduga. Link only has to defeat each mini-boss specimen once for it to count as the Blood Moon makes it next to impossible to defeat every specimens of Hinox and Talus in Hyrule before they are revived by Ganon during a Blood Moon. However it is possible to defeat every single Molduga as their are only 4 living within Gerudo Desert before they are revived during a Blood Moon as all four are located in a single region. In contrast there are 40 Talus and 40 Hinox specimens in Hyrule, which includes all their variants. Obtaining the medals is entirely optional and Link can accomplish it even before speaking to Kilton.