The Eight Straight Teeth of Ashadon is a location in the Landscape Campaign.
The Eight Straight Teeth of Ashadon (or ESTOA), is the name given to a magically formed mountain range to the southeast of Grem's Slide. It is named after the red dragon that has inhabitied the range for most of historically recorded time.
Each mountain has been given a number rather than a name. In the episode Starstone, Blue Light, All Night, All Right, the adventurers entered the mountain range looking for information about the dragonborn armies. A comet shot out of the sky and crashed into the Third Tooth, and revealed the long lost and very well hidden prison of Tulan , a tiefling lich.