The ankheg is a huge, insectoid monster with many slender limbs and large antennae; usually colored bright green to dark brown. The creatures live underground and hunt prey from below.

Living in warm climates, the ankheg dwells in partially collapsed burrows usually around 40 feet underground. Ankheg usually hunt in forests or grasslands where their prey will wander into its traps. If an area becomes too barren, the ankheg will move on to other, more lucrative areas. Ankheg tunnels are sometimes filled with the remains of victims, eggs, or chitin. Their tunnels are between 60 to 150 feet long and 5 feet high. Hollow tunnel ends are normally used for lair purposes, such as sleeping or hibernation.

A harvested ankheg shell can weigh up to 100 lbs. Skilled armorers can then forge armor from these shells. This process usually takes three days to complete, and the result is a fine suit of bright green armor. Ankheg armor is very nearly as effective as full plate mail; but weighs considerably less and can be worn by warriors who usually cannot wear such heavy armor.