The ahnkheg was created by artist Erol Otus and first appeared in Dragon magazine in 1977.
An ankheg is described as having six legs and a many-segmented body, all covered in a brown chitinous exoskeleton. The head has black compound eyes, mandibles capable of snapping small trees, and antennae. Usually, ankhegs do not create tunnels, and simply burrow down into the ground. However, they are able to make tunnels if they dig slowly. The ankheg is a huge insectoid monster with many slender limbs and large antennae. It burrowes underground and hunts from below. When seriously pressed, it can spit acid. Spitting acid is usually a last resort, as it cannot digest food for several hours afterwards. Ankhegs are around 10 feet long and weigh 800 pounds.
The ankheg iss an ambush predator that wais around 5–10 feet underground for prey to wander into position. The attack is quick, as the prey is crushed and ground in its mandibles and assaulted with acidic digestive enzymes. If a foe proves too difficult, the ankheg can also squirt acid to take it down.
So I imagine that the Ankheg is a lot like the Antlion. Maybe the party of adventurers are making their way through the Underdark and start moving through some dry caves with sandy floors. They might find the way hard-going. Think about the last time you went to the beach and had to slog through loose, ankle deep sand. It’s slow going and not the best footing for exploration.
Off to the sides of the dry cave network the keen party would notice some burrows made by the Ankheg. Burrows are generally long tunnels, perhaps with a widened
spot at some point, created by creatures as shelters. Only very large burrows are big enough for characters to enter; unfortunately, very large burrows are usually created by very large creatures that do not always react kindly to the intrusion. Burrows are generally excavated from dirt, but certain monsters can create burrows in solid stone. A burrow is generally no bigger in diameter than the creature who created it, although a larger chamber is often excavated at the burrow’s deepest end.
At some point, the party will enter a cave that exists simply to act as a trap for intruders. The Ankheg will have burrowed down into the center of the of room, leaving a large divet in the sandy floor of the room. If the party starts to examine, they end up sliding down into the trap … and well … watch the videos below for ideas …