Facet

A facet is a five-foot humanoid, nearly featureless, made of salt crystals and seemingly drawn in hard, angular lines. It never communicates with outsiders, or visibly with its own kind.

Facets are seldom alone, and their danger lies in draining water from anything that holds it. Each strikes with two thin limbs for 1d4 damage apiece. Any creature that is partly water (nearly every living thing except elementals of earth, fire or air) automatically loses another 1d4 the following round as the wound dries out, leaving the cracked, chapped welts that mark a facet's victims. Someone already bleeding from other wounds takes 1d6 from the strike instead, as salt stings the open cuts, though the follow-up damage stays 1d4. Against beings made wholly or largely of water, like water elementals, both the strike and the follow-up rise to 2d4.

The follow-up damage is what feeds the facet. When the water it has drained this way reaches its own maximum hit point total, the creature splits in two, spending a full round in which neither half can act. Each new facet has half the original's Hit Dice and needs about a week to regrow to full strength. The original can keep fighting but usually cannot split again, and the offspring cannot split until it is fully grown, so in one battle a band of facets can at most roughly double. Create water cast on a facet lets it split at once if it is able. Transmute water to dust kills one outright, combined or not, if it fails its save.

Up to five facets can merge into one large creature over 1d3 rounds, and separating takes as long. A combined facet's Hit Dice equal the total of its members (five make a 15 HD giant), its THAC0 matches the new Hit Dice, and its damage is the sum of all members, so a five-facet creature has THAC0 5 and deals 5d4 per attack. Two or three members make a size L creature; four or five make size H. Other statistics are unchanged.

Think of all facets as a single being with many detachable limbs. Each one is part of every other; they never talk, yet move in perfect coordination. Rumor speaks of a master facet, perhaps the first, directing the rest, which would offer hope of stopping them, but the evidence suggests every facet is an equal fragment of one shared consciousness.

They come from the Quasielemental Plane of Salt, where a vast host is massing. Where Salt meets Water lies a briny border sea, and there roughly a third of all facets are slowly crawling forward, soaking up liquid in an ever-growing tide; the rest wait deeper in their plane, though in time all seem bound for the front. As they absorb water, the Plane of Water pours more into the border to replace it. The amounts are close to infinite, but the drain on Water's essence is real, and since water lets facets breed, the threat keeps growing. The natives of Water may not notice the war for a long time.

Salt through and through, a facet exists only to absorb water, which feeds it, drives its endless thirst, and lets it reproduce. Most split only once in a lifetime, but one in five can do it twice and one in 20 three times, so the population can always grow. As they meet richer water near the border, observers reckon their numbers double every three weeks, and someone will need to deal with them before Water, and perhaps more of the multiverse, pays the price.