Publisher's description:

The powerful third volume of the Crowthistle Chronicles - an effortlessly rich and beautifully crafted fantasy feast
On the misty, pine-clad slopes of the western highlands five princes go hunting – but the mountains are perilous and they clash with unexpected foes. To the north, a burrower digs its way through a labyrinth of underground caverns; there is no knowing what it is, how it came there, or where it is going.
The great golden sword Fallowblade is displayed above the mantelshelf on the house of Lord Avalloc Stormbringer. A weapon almost legendary by reputation, it was used in days of yore to destroy the goblin hordes. Asrāthiel Stormbringer, powerful weathermage, is learning swordplay so that one day she might wield the magnificent blade, doing justice to this family heirloon . . .
. . . While in the south, a tyrant rages and deceives, and hatches inimical plots. Five princes, an enigmatic burrower, a weathermaster and a fabulous sword – these elements come together to weave the surprising story of WEATHERWITCH.