The Hammerpede (also known as the CobraBurster, Milbworm, Cobralien or Cobrahugger) is formed when the Engineers' urns spill Black Liquid on the indigenous worms of LV-223. Whether they can be formed from other species of worm on other planets is unknown.
When the Prometheus arrived on LV-223, the crew, led by Dr. Shaw and Holloway discovered an Engineer spacecraft, which they explored. When they disturbed a room containing urns of the Black Liquid pathogen, the Liquid began to leak out of the urns onto the floor, infecting several worms which mutated into Hammerpedes.
Millburn and Fifield, two members of the crew, got lost and managed to reach the same urn room, where they discovered two Hammerpedes. One of them rose and scared Fifield but Millburn looked upon it, fascinated. The creature attacked him, constricting his arm. Fifield tried to help Millburn, but only succeeded in breaking his arm. In a further attempt to save Millburn, Fifield cut off the Hammerpede's head, causing its acidic blood to spray on Fifield. The Hammerpede then regrew its head, showing its regenerative abilities and slipped into Millburn's suit through a hole made by his protruding bone, entering his mouth and subduing him.
Meanwhile, the Hammerpede's acid blood began melting Fifield's helmet, causing him to fall into the Black Liquid on the floor, which would later begin to transform him into a grotesque mutant. Later when the rest of the crew goes to save the two members, they discovered the Hammerpede exiting from a dead Millburn, escaping. What happened to the two Hammerpedes later is unknown, but it is possible that they were killed when the Engineer ship they lived in crashed.
The Hammerpedes are very similar to real-life worms, but they are much larger. They were pale in color and had serpent-like bodies up to 4 feet long. Their crests are very similar to those possessed by cobras (which is why they are sometimes referred to as Cobrabursters or Cobraliens). These crests could be folded in and out around the creature's "head". Their "head" was similar to that of a Facehugger, and they possessed the same acidic blood. They possessed incredible strength, able to break bones rather easily as was demonstrated when Fifield attempted to remove one from Millburn's forearm. They also possessed the ability to rapidly regenerate severed parts in a matter of seconds as shown when Fifield attempted to decapitate one, only to have its head quickly regenerate.
- The origin of the worms that the Hammerpedes mutated from has been debated constantly; some say they could have been native to LV-223, which is unlikely due to the atmosphere. Others think that the Engineers brought them to LV-223, possibly for testing the Black Liquid (though this is unlikely, as the Engineer ship they lived in had been on LV-223 for 2,000 years). Another possible explanation is that they may have been aboard the Prometheus and was under the feet of one of the crew members; however the worms then should have fallen off sooner if not killed by being exposed to the atmosphere, and even so, they would have most likely died of starvation aboard the Prometheus long before in reached LV-223.