The Flathead Mountains are a towering range in the Eastlands from north to south, forming the eastern border of the Frigid River Valley. Their tallest peak is Mount Foobia, reaching the top of the world. Beyond the mountains, the Fenshire Swamp extends to the edge of the world.

Near the southern end of the range, the Zorbel Pass permits passage to the Fublio Valley. To the north the Flathead Fjord separates the range from the Gray Mountains.

The Mountains contain the Enchanters' Retreat.

Dimwit Flathead had a hidden vault 7 miles under the Mountains, accessible by a chain of 63 secret teleport spells.