Final Gate (Forgotten Realms: The Last Mythal, Book 3)2006
(Final Gate)
by Richard Baker
In the hands of an elf high-mage, the fabled mythals are Faerun's most potent sources of magical power. But in the hands of a demon princess from a forgotten epoch, they're the most powerful weapons imaginable.From the Paperback edition.
— from OpenLibrary
2 editions at OpenLibrary