Oy first appeared in the Dark Tower novel The Waste Lands. He is the pet and best friend of Jake Chambers and a twinner of Billy the Bumbler.
Oy was created for the Dark Tower novels by Stephen King.
Billy bumblers, or throcken, are a common species in Mid-World. They are described as being smarter than dogs, and can parrot human speech. In some cases this goes beyond mere mimicry, and more intelligent bumblers have a limited capacity for speech. Oy is one of these bumblers, and it is hinted at that he was cast out by his pack because of his advanced intelligence and verbal proficiency.
Major Story Arcs
The Long Road Home
In the Marvel series Dark Tower: The Long Road Home, Oy appears to Roland in Maerlyn's Grapefruit, impaled on a branch and calling out his name. As in the novels, the significance of this foreshadowing passes Roland by, and he is unaware that he watching the future death of a member of his ka-tet.
Billy the Bumbler
In the series Dark Tower: The Gunslinger - The Journey Begins, Roland meets a bumbler who is a twinner or alternate version of Oy named Billy. Billy's story deliberately mirrors Oy's life, to strengthen the idea that they are twinners. When Roland Deschain first finds Billy, he is licking his dead masters face, just as Oy did after Jake's death in the novel The Dark Tower. Their deaths are also intentionally similar - Billy's final scene, in which he is impaled on a branch by a No-Man while defending Roland and Susan is almost exactly the same as Oy's own death, defending his dinh from Mordred.
Powers and Abilities
Like all bumblers, Oy can be vicious if provoked, having very sharp claws and teeth. He and Jake also share a form of telepathy, and are able to share each other's thoughts and feelings.
In the novels, this extends to actual body swapping, which the pair use to overcome a mind trap on their way to Fedic.
In Other Media
In the Dark Tower novels, Oy is a central character. When he first approaches Jake, he is injured, having been rejected by his own kind. The two soon form a deep bond, and Oy goes on to become a member of the gang, traveling with them right through to the last book in the series, The Dark Tower.