Whilst the oceans’ depths and vast tracts of the world are unexplored, some discoveries indicate that the ground beneath our feet may be teeming with secrets all its own.
Initially discovered in the 1750s within mines around the Ruhr basin in Germany, these subterranean creatures are found buried in and surrounded entirely by veins of bituminous coal. Usually alone - occasionally in pairs or, at most, groups of three - they initially appear to be small clumps of greasy, tarry coal, having dimensions similar to those of marbles although, naturally, much rougher and far more irregularly shaped. The unusual circumstances in which they are found gave rise to their original name ‘Grüberlings’; a variant on the Bavarian name Gruber, which denoted someone from a mine or pit. This was later anglicised to the more frequently used ‘Grubberlings’, perhaps through a mistaken association between their destructive behaviour and the definition of grubber as someone who is greedy or avaricious.
Lying dormant within the coalface, even if dislodged somewhat roughly, the first indication that Grubberlings are not merely rocks is the prickly and persistent heat that their bodies give off. They feel too-warm to the touch - like a pebble picked from the beach on a bright, sunny day - and make the skin tingle, though this latter may be the frisson, conscious or not, from recognising the dangers of such close contact. Obviously if these were the only characteristics which differentiated them from the coal then they would likely not merit much time and attention, and perhaps that would be to our advantage, but this camouflage provides a cover for something which can be as extraordinary as it is unfeelingly brutal. If a Grubberling is jarred too sharply, if the blow which strikes the coalface lands too close or if they are deliberately imperilled, they start into action with a single-minded surety and a speed which belies their previously absolute inertia: They begin to feed in an awful frenzy.
Almost preternaturally passive beforehand, people have even taken video of themselves juggling them, an awoken Grubberling exhibits an implacable will. Unclasping and unfolding two short, forklike arms with wriggling, prehensile tines they expose a black maw with rows of flat, grinding teeth. Grasping for whatever is in front of them they either pull it into their mouth and grind it down, sucking it into themselves, or latch onto it and pull themselves close enough to bite down. Their bite is inexplicably strong (If induced to or situated such that it is within their grasp a Grubberling will bite through diamond as effortlessly as through its native coal) and they feed unceasingly and remorselessly, quickly eating through any pick or machine that has disturbed them and on to the extremities of any unlucky person who gets too close or is too careless to retreat at haste. Some have died as a result of an encounter with one or more of them, of course, but these are limited to the unfortunates who have either some vital part of themselves eaten away or who have bled to death from the trauma, alone in the deep and the dark and far away from help.
Whatever a Grubberlings’ meal - and people have variously attempted to gorge them on a variety of minerals, meats and more exotic matter in hopes of unlocking some strange alchemy by which these creatures’ voracious appetites can be exploited for something other than wholesale carnage - the pace of their feeding means that they quickly reach capacity, distending jaggedly until they reach approximately the size of an adult fist. Having, apparently, either no desire or no ability to stop eating, they will continue to feed past this point, soon becoming so full that they literally burst and die. The rupturing is aggressively, explosively self-destructive, with the Grubberling entirely reduced to misshapen shards of the dark grey, rocky substance from which they were formed, a material which exhibits all the properties and characteristics of the bituminous coal wherefrom the creatures are usually hewn. Fortunately, the scarcity of Grubberlings limits the danger they present, since even the larger triad clusters can only do so much damage before their ravening takes its toll on their bodies.
If a frenzied Grubberling is trapped or restrained in such a way as to prevent it from feeding, for instance if it is placed within a smooth spherical vessel where it cannot gain purchase with its arms or bite, it will begin to devour itself instead. It will, if able, begin by gnawing off its arms, eating through them with as little pause as if they were anything else in its path. Then, or else if its arms have been pinned away, it will twist and contort until its insides are protruding out of its mouth and begin to eat those. It is a singularly unpleasant sight, with the increasing damage allowing the Grubberling to pull more and more of itself into its pulverising jaws until, variously deformed and disfigured, it is a relief to see the mauling cease; to see the thing finally, mercifully, surrender to its death.
Beyond these grotesque displays their habits, ecology and lifecycles of Grubberlings are hidden entirely from the world. No larger groups have been discovered, no burrows or warrens or habitats or even signs they have ever moved from where they are found. As a result, some have theorised that they are terrifically ancient, that they do not traverse the seams of the coal they inhabit but were either present or created there in the same crushing furnaces as the rock itself. Others believe that the sole purpose they fulfil with their brief lives suggests a role in some rigid hierarchy, that the Grubberlings which have been discovered serve as some sort of defensive mechanism around a centralised nest where other variants of what might be a hive species perform similarly singular functions in service of a larger Queen or some such. Perhaps, goes the postulation, there is a vast underground ecosystem filled with beasts that, if threatened, would spill out of the scars and gouges that human industry has cut into the surface of the earth, devouring our civilisations and making a palimpsest of a world we once called our own.