Ravine grubs are like maggots, ranging in size from a few centimeters to half a meter long. They are usually dark brown or black in colour, although some have carapaces that shade to a deep blue, and their hides are rubbery and flexible, like leather, except at the front, where they taper off to an iron-hard point. They feed and drink through a ring of small round mouths which form a ring about halfway down their bodies.

They can flex and hop up to five meters from a standing start, but are otherwise quite slow moving, and usually don't jump unless threatened or in a feeding frenzy. Their preferred habitat is at the bottom of deep ravines in glaciers and frozen areas close to tundra and mountains, and they can dig into solid ice quickly, remaining dormant for decades if needed.

This habit of drilling tunnels through the ice is also their main method of trapping prey, they will riddle the walls of the ravine with small tunnels from the top all the way to the bottom, as a woodworm makes holes in wood, and dig higher tunnels the further away from their nest they get.

This weakens the underlying ice so that if an animal or explorer sets foot even nearby the ravine, the ice collapses under their weight, forming a steep slide which drops them straight down into the middle of the grubs. The grubs also secrete a type of antifreeze compound which not only prevents refreezing of their tunnels but lubricates the wormholes when they collapse, making the slush slippery.

Once prey falls into the grubs' nest, a feeding frenzy commences, with scores or hundreds of ravine grubs burrowing into their victim and consuming them from the inside out. Cannibalism is also not unusual in these feeding balls, and the grubs consume everything down to the bone, and even the bone itself.

The difficulty of spotting ravines in icy terrain multiplies the risk these creatures represent, as a traveller might not so much as be aware they're approaching a rift before they start to slide downwards!

Over time successive generations of ravine grubs widen small cracks into broad canyons, and rumours persist of giant ravine grubs that burrow from ravine to ravine to open new hunting grounds for these creatures. These grubs aren't amphibious and will quickly sink and drown in water, leading them to occupy glaciers and frozen rivers as well as mountain ice.