Rank: Varies, when isolated D-, can reach up to an A+ in a same leveled host.
Order: Geoderma
Height: Varies, depending on size and rank of host. 2 inches to 4 feet (at head).
Length: Varies, depending on size and rank of host. 6 inches to 16 feet.
Weight: Varies, depending on size and rank of host. 10 ounces to 275 pounds.

A very primitive member of the Geoderma family, the NucleoWurm possesses a very thin skin, and a tough, metal-tipped drill bit on the end of its tongue for boring into the tough hides and calcium shields of larger kreatures. As the miniscule young living in nutrient rich bogs, absorbing food, metallic elements, and energy. NucleoWurms enter their hosts as they drink, and they then bore through the esophagus and other body tissues until they reach the nucleus. There, they latch on, leeching off of the larger kreature's KE and growing. Their maximum size is determined both by the amount of energy to exploit and the size of their host. They use their fleshy tendrils to probe around for food in their ponds, and, when in a host, to find the nucleus. When inside, they use their gills to extract oxygen straight from the bloodstream.

Hermaphrodites, they reproduce by spawning their eggs directly into the host's blood stream, where they hatch in the heart. From there, some larvae move to the lungs, and then up to the host's mouth. Others go to the excretory system, to be deposited in another body of water. Meanwhile, the adult NucleoWurm secretes hormones which cause the host to be increasingly aggressive, to further their spread by fluid exchange.

After a period of a few weeks, the NucleoWurm bleeds their host dry, killing the host, itself, and any lingering young. By this time, however, the parasite has already spread to more hosts.

NucleoWurm larvae, genetically modified to be both sterile and more voracious, are occasionally used by unscrupulous Kreature Tamers to sabotage their competitors, and are notoriously difficult to detect.

Both in the wild and in their usage in competitions, they're almost universally hated, and numerous campaigns have been made to eradicate them, with little success.