|Book(s)|| A Game of Thrones (appears)|
A Clash of Kings (mentioned)
A Feast for Crows (mentioned)
Joss Stilwood is the squire of Ser Gregor Clegane.
A Game of Thrones
A Clash of Kings
According to the story Chiswyck tells, Joss was part of Gregor's party returning from the tourney when an overflowing river detoured the group to a nearby alehouse. There Gregor proceeded to rape the innkeep's daughter while Raff the Sweetling killed his son. Joss eventually raped the young girl too.
A Feast for Crows
Qyburn mentions to Cersei Lannister that he questioned Gregor's squire, who informed him that Gregor constantly suffers from extreme headaches and consumes vast quantities of milk of the poppy to try and dull the pain.