Thornado is a dragon that appeared in the Riders of Berk series.

He's a Thunder Drum and Stoick's own dragon. At the beginning, he was causing problems to the fishermen's nets and ships of Berk. Stoick and Hiccup , on Toothless' back, reaches Mulch and Bucket's ship where the Thunder Drum and Stoick wrestles in the water. Stoick admired how strong the dragon was and declared that he wanted to tame and train him, in order to make it his dragon. Back in Berk, chained and muzzled, the dragon doesn't seem to trust Stoick, despite how hard he's trying to let the dragon see he can be trusted. The two wrestles again and the viking decides to ride him, tamed of not. Thornado is able to send Stoick away and ascapes, with the teen riders and the chief viking searching after him.

Thornado is found with another Thunder Drum, a violent one that is injured and that Thornado was protecting and feeding. Hiccup and Toothless fly back to Berk to find help for this dragon while Stoick remains with the two. As he was trying to show that he wasn't a danger, a group of wild boars arrive, hungry, intentioned to eat the violet dragon. Both Stoick and Thornado fight the boars and win, with the viking gaining the dragon's trust.