Thriff may be in a cold climate, but you'll need to write yourself a searing hot plan to save it.
You need to find a way to make the Glyph of Warding that Orkan left in the snow permanent.
Orkan's journal mentions Yonking a Girgol spell on a nearby "mountain". (Yonk enhances magic and Girgol stops time.)
That's not a mountain ... that's a volcano, full of molten rock!