Ultimate Magic — T.A. Barron

Avalon is on the verge of total destruction: an army of warriors, a swarm of fire dragons, and a lethal plague are all laying waste to Merlin s beloved land. But Merlin is nowhere to be found. Leading the fight in his place is Basil, the once tiny lizard who is now the most powerful dragon in Avalon.

But to restore peace, the mastermind behind this chaos, Doomraga, will need to be discovered and destroyed before his power grows stronger and Avalon and its inhabitants are beyond saving. For Basil to triumph, he and his friends may need to make the ultimate sacrifice.