Vermithor, who was briefly shown in the first season as Daemon tries to claim it but does not succeed in doing so, is a furious beast, known to burn anyone who dares to tame it

Vermithor in House of the Dragon
The first season `House Of The Dragon` ended on a high note with Lucerys`s death, which planted the seeds of conflict between the Red and Green councils of House Targaryen. Lucerys, son of Queen Rhaenyra was killed in a brutal encounter by Aemond’s dragon Vhagar. The second season has been running at a slow pace with Daemon in Harrenhal trying to get an army, while Rhaenyra battles sexist council members and a way to fight the war sans dragons.
The season three episode witnessed Rhaenys Valaryon and her dragon Meleys head out to stop Ser Criston Cole and his men at Rooks Rest. However, she is taken aback by a surprise attack from Aegon who arrives on his own and charges with Sunfyre. While Aegon is injured, Rhaenys falls to her death after Vhagar kills Meleys. Aemond sits on the throne after being elected by the council.