Ashfire is an island mentioned in book 2, and is visited by Corr and Crown, when they are looking for sepia in book 5. It is home to a volcano (termed "fire mountain"). The island is somewhere to the west of Mistmantle and is far away. The water on Ashfire is poisonous to all except Ashfire natives.
Urchin's mother Almond is from Ashfire, as well as Queen Cedar. In the fifth book, Sepia ends up on Ashfire after being swept there by a rage tide.