|This article contains canon information corresponding to the Tales of Arcadia franchise. That means all information in this article is true and has appeared/been validated officialy on-screen.|
Gatto is a selfish and unpleasant being; he accumulates treasures only to attract others and devour them. He is capable of devouring his own subordinates without reason.
After learning than Gatto possessed the Birthstone of Gunmar, Jim Lake Jr., Toby Domzalski, Claire Nuñez, Blinky, and AAARRRGGHH!!! go to get it. When the group first meet Gatto, he gives them a challenging riddle to determine if they get what they came for, or if he gets to eat them. The riddle is, “What begins but has no end, and ends all that begins?”
Claire correctly answers that it is "Death", Gatto remarked no one has surpassed his challenge and lived to tell about it. As Volcanic Trolls surround them, Blinky realizes that Gatto was never going to honor his end of the bargain and that the gigantic troll hoards treasure to lure others into his belly; Gatto shamelessly says a mountain needs to eat. He proceeds to devour Toby and Blinky while his henchmen chase after the others. However, both managed to find the Birthstone in his stomach and gave him indigestion with tacos in order to escape via his "backdoor".
Later, Jim, sans his amulet comes before Gatto and demands the Kairosect. Amused by the demand and still bitter about being fed tacos, Gatto demanded a reason to let him live. The Trollhunter dared him to answer his riddle, "What do you call cheese that isn't yours?" Though Gatto correctly answers, "Nacho cheese", Jim then summons the other Trollhunters, who appear through a portal conjured by Claire's Shadow Staff, before entering Gatto's mouth. Annoyed that he's being burgled again, Gatto orders his trolls into his belly to stop them. However, they were unable to stop the Trollhunters from obtaining the Kairosect and feeding Gatto a burrito more spicier than the last. As the Trollhunters flee, Gatto curses Jim.
Gatto is shown as a member of the Troll Tribunal. He attends the meeting using a projection of his face made of floating rocks. He is one of the Tribunal members that voted for the Killahead Bridge to be hidden away indefinitely.
When Jim was later on trial by the Tribunal for treason, as Queen Usurna forced Toby to be Jim's attorney in accordance with troll law, Toby tried to get Gatto removed from the jury due his biased stance against Jim but was denied.
Blinky and AAARRGGHH!!! arrive at the volcano to recruit the Volcanic Trolls for their battle against Gunmar and Morgana. Gatto refuses to help, despite Blinky’s warnings that the entire world will be destroyed. However, eventually the Volcanic Trolls decide to help them when the Eternal Night comes.