Grant's Onix first appeared when Grant was battling against Viola and her Surskit at the Battle Chateau. During the battle, Viola used the ice floor strategy she previously used in her Gym Battle against Ash. Unfortunately, Onix was able to withstand Surkit's attacks and trapped it with its Rock Tomb attack. Once it was trapped, Onix single handedly defeated Surskit with the combination of Rock Polish and Flash Cannon. After seeing the battle between Onix, who used the Rock Tomb combo and Surskit, Ash wanted to train for his Gym Battle against Grant.
Onix was later used in the Gym Battle against Ash. It was the first Pokémon Grant used and it went up against Ash's Froakie. Onix started off with Flash Cannon, then boosted its speed with Rock Polish, but somehow got confused with Froakie's Double Team. While trying to find the right one, it used Rock Tomb. However, to Grant and Onix's surprise, Froakie used the tactic, the Rock Tomb Climb, to climb higher and Froakie damaged Onix off with a direct hit with Water Pulse. Onix tried to retaliate with Iron Tail, but Froakie jumped on Onix and repeated its attack, thus making Ash win the first match.
Unshō Ishizuka (Japanese and English)