Wizards of Once: Never and Forever by Cressida Cowell
Can Xar and Wish unite their worlds in time to save the Wildwoods? Will it be Never or Forever? The final book in the magical The Wizards of Once series.
Xar and Wish have found the ingredients for the Spell-to-get-rid-of-Witches. Now the Kingwitch is calling them to the lake of the lost. But first they must mix the potion in the Cup of Second Chances