Mercurial Slime

A colony of mercurial slime looks like a big, wobbling globe of liquid silver floating through the void between worlds. Colonies often travel in loose groups but keep at least 30 feet apart, so only one attacks a ship at a time while the others may drift into its escape routes. Starhelm crews dread it as quick, mindless and lethal.

The slime has no sense organs, yet it homes in on sound and is drawn to light; inside an atmosphere it also feels motion through air currents. Its whole mass is laced with acid that does the job of blood and stomach juices. On living flesh that acid deals 5d10. Any inorganic item it touches must save vs. acid at -2, and a weapon striking it must make that save before damage is rolled, dissolving harmlessly if it fails.

A ship that brushes the slime must save vs. acid. On a failure the slime makes a normal attack roll, and a hit damages the vessel like a heavy ballista.

Light glancing off its silver skin sometimes ripples into beautiful colors. Anyone who gazes at the display is entranced as if by a 4th-level hypnotic pattern, and only a full round of violent shaking breaks the spell.

Because it is not organic, nature-control magic such as charm plant or charm animal has no effect. Fire, cold and electricity cannot hurt it either, though magic missile can.

Mercurial slime is mindless. It cannot communicate and has no organization beyond its colony, simply roaming the void in search of food.

It reproduces by fission while digesting living tissue. Each hit on an organic target has a flat 1% chance of splitting it into two full-sized slimes on the spot, and the victim takes an extra 5d10.

The slime turns light, even starlight, into thrust and can reach starhelm speeds. It needs no air, but it can never land on a world, because gravity shreds it into a mist that quickly vanishes.

Attempts to harness it as a living ship engine have failed, since it attacks any container, forcing a cumulative -2 save vs. acid every round. Alchemists who want its acid have the same problem with vials. Some sages think it is an ordinary slime or jelly from the worlds below, carried into space and changed. Others call it a plague from gods who want mortals off the spacelanes, a theory no cleric supports. A few elven scholars suspect it is a weapon left over from a great war against the orc hordes.