Frost worm

Frost worms were massive, worm-like creatures that terrorized wintery environments.

Description
The average frost worm was about long and  in diameter, and weighed about, however some specimens could grow to truly gargantuan proportions. Their skin was a very pale blue, and their heads were marked by huge mandibles and a nodule from which they emitted a trilling noise.

Abilities
A frost worm's signature trill was used to stun its prey. This acted as a sonically-induced compulsion to stand still for as long as the trilling noise was audible, thus making an affected creature into an easy target. The trill was effective at up to, and even being attacked by the worm or violently shaken to their senses only sometimes allowed a victim to snap out of their trance.

Merely touching a frost worm could be injurious as their bodies generated an intense chill, which meant that any attack from a frost worm was especially dangerous. They could also weaponize their natural cold by expelling it as a breath attack that could reach targets up to away. Furthermore, a slain frost worm's body instantly froze into ice before shattering in a mighty explosion that threatened to freeze and shred everything within a radius.

Behavior
A frost worm waited for prey while hidden in snow banks. When a target got close, the worm would stun it with a trill and then attack the immobile target with its breath attack or with a powerful bite of its mandibled jaws.

They hated fire, and were afraid of it.

Ecology
Frost worms were well-adapted to their native arctic environs as they were both impervious to the cold and excellent at camouflaging with snow. They could burrow through the snow, ice, and frozen earth of their territories, although not through solid rock. Their tunnels were stable and about in diameter, making them useable by other creatures. The worms themselves generally remained in their underground tunnels, and had excellent low-light and darkvision to assist with this. Their tunnels looped and cross-crossed themselves, creating confusing, honeycombed labyrinths beneath their hunting grounds.

In general, a frost worm only came to the surface to hunt or attack their prey. They hunted mammoths, moose, polar bears, seals, walruses, yaks, and the occasional humanoid or giant. They preferred to attack smaller groups, usually of no more than six individuals.

Frost worm eggs were easy to mistake for chunks of oval-shaped ice. They lived and hunted alone from the moment they hatched, and grew to maturity in three to five years.

Some sages argued that frost worms were related to purple worms and/or to remorhazes. Regardless of the truth, frost worms were known to attack remorhazes on sight, even though a remorhaz was usually the victor in such battles. These fights could turn into titanic clashes that devastated the surrounding area.

Habitats
Frost worms could be found in cold regions and mountains, including the Galena Mountains in the Cold Lands and the Thunder Peaks in the Eastern Heartlands. They could even be found outside the Material Plane in the Elemental Plane of Cold, the Iron Wastes of the Abyss, and an air elemental variant of the frost worm could be found in the Elemental Plane of Air.

Uses
It was possible to capture and train young frost worms. They could be trained not to attack anyone who looked like an ally, or to attack only when an intruder triggered some kind of trap. Captive frost worms could also be trained to work in pairs rather than alone. Some arctic tribal communities trained them as protectors or mounts, although riding a frost worm required a magically cold-resistant saddle.

Tanned frost worm hide could be made into a dazzling white-colored leather.

Notable
As of the, a frost worm had claimed the western side of the ruined city of Skelem as its feeding grounds.

Appearances

 * Adventures
 * Mysteries of the Moonsea: "Eastern Moonsea adventure arc"