|TV series||Season 1|
A Game of Thrones
Joss squires for Ser Gregor Clegane during the Hand's tourney in King's Landing. When Gregor is unhorsed by Ser Loras Tyrell, he calls for his squire to bring his sword, which the Mountain then uses to kill the horse.
A Clash of Kings
According to Chiswyck, an overflowing river detoured the Mountain's men to a nearby alehouse while they were returning from the tourney. Rafford urged Joss to loss his virginity to the brewer's young daughter, Layna. When the brewer objected, Gregor and his men raped the girl. Gregor also stabbed the brewer's son in the belly when he tried to intervene.
A Feast for Crows
Qyburn mentions to Queen 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.