Jormungar

A jormungar in the Borean Tundra.

Jormungar concept art.

Jormungar by Red Knuckle, colored version of the above art.

Jormungar are creatures that can be encountered in Northrend in World of Warcraft: Wrath of the Lich King. They have muscular, flattened bodies with rows of crystalline spines along either flank.

From the official  World of Warcraft Community Site Wrath of the Lich King — Bestiary:

The fiercely aggressive jormungar are a marvel of evolution, possessing rows of chisel-like teeth capable of boring through solid rock, as well as muscular, flattened bodies well adapted to rapid underground navigation.

Legends tell of the nerubians' using the jormungar as creatures of labor, forcing them to carve massive tunnels through Northrend's subterranean ice and lay the groundwork for the nerubians' ancient civilization. With the fall of the nerubian empire, swarms of rogue jormungar ran amok, drilling through the region's permafrost, attacking surface dwellers, and devouring everything in their path.

Notable jormungar

•  Acidmaw
•  Dreadscale
•  Jormuttar
•  Rattlebore
•  Yggdras

Myth

The name is a reference to or inspired by the World Serpent of Norse mythology, Jörmungandr, which was said to be so large that its tail had to be stuffed into its mouth to prevent it growing larger than the world. Jörmungandr was one of the three children of Loki, the mischievous frost giant in Norse mythology. In the quest Quest:The Slithering Darkness, the quest giver says that the jormungar are the children of Loken, whose name is inspired by Loki.

Speculation

This article or section includes speculation, observations or opinions possibly supported by lore or by Blizzard officials. It should not be taken as representing official lore.

It is speculated (given the carvings on the pillars around Uldum) that this worm, or one like it, escaped from the Uldum complex in Tanaris. The door to the complex seems to have a giant hole in it, sticking outward.

• There are several holes with this theory now that more information on the worms is available from the official website. Firstly, it is said that there are many jormungar and they have been around since the early days of the nerubians. Second, they are native to Northrend. Last, but not least, it is stated they are able to effortlessly bore through solid rock and ice. It would make no sense to attempt to hold jorumungar in a stone prison. They would simply tunnel their way out.