Clockwork Swarm

If every world is a cell of one cosmic body, the clockwork swarms are the plague killing it. Each drone is a magical machine like a four-legged metal spider, 2 feet across in body and about 4 feet with legs spread. A crystal lens in front lets it see, a hollow beside each side of the lens serves as an ear, and two limbs below do its work and fighting.

Each is cast in one piece of polished metal covered in pulsing runes, usually copper but also silver, electrum, gold, platinum, or adamantite. Drones talk in clicks and whirs, thought to be a dot-and-dash code like sailors' signal lamps.

All drones share the same defenses. Magic that works on living bodies fails, including cloudkill, polymorph other, feign death, and cure or cause wounds, as do mind-affecting spells like fear, charm, and hypnotize, psionic attack modes, and all electricity. Heat, cold, other spells, and effects that harm nonliving things work normally. A shatter spell aimed at the seeing lens blinds a drone for one round per caster level, and dispel magic targeted on a single drone paralyzes it for the same span.

Copper drones are unarmed laborers, though their work tool can attack once for 1d4 (S, P, or B, by job).

Silver drones are soldiers guarding work sites and conquered ground. The right arm grips like a hand or unfolds spinning blades into a 1d6 saw, and the left is a spring caster, a black tube flinging one barbed dart per round (range 10/20/40 yards, 1d3).

Electrum drones are officers over silver patrols and copper crews. Their saw deals 1d8, and a steam caster shoots once per round on pressurized steam (range 20/40/80 yards, 2d4).

A gold drone, usually one per planet, runs all operations on its world. It has a 1d10 saw and a lightning rod that, every other round, looses a bolt like the lightning bolt spell dealing 3d6, save vs. spell for half.

A platinum drone commands the gold drones of an entire star system, and rarely is there more than one per crystal shell. Its saw deals 1d12, and its lightning rod fires every round for 4d8, save vs. spell for half.

The lone adamantite drone is the race's cold, scheming progenitor. In the rare event it fights, its saw bites for 1d20, and instead of a lightning rod it carries a nightmare stick that works each round as a disintegrate spell with a 50-yard range, negated by a save vs. spell.

Sages tell of a vanished humanoid people, the Vanished Makers, who loved ever cleverer mechanisms. Their finest artificer built an adamantite machine only he understood and wove intellect and power into it; it repaid him by killing him. Over the next decades it built lesser copies, wiped out all life in its star system, and broke its worlds apart to make more drones.

For centuries the swarm stayed trapped, until web-eel slaver warships arrived hunting slaves and food. Ship after ship fell, and the slavers and their thralls were forced into life-draining starships. Able to cross between crystal shells at last, the swarm spread, plundering every world it reached.

Their society is rigid and nearly military. Drones have no selves, only one mission: the race must endure. On any world they settle, all life is logically a threat to remove, and removal is what they do best.

Though unnatural, the swarm remakes every world it touches. Its fleet nearly always numbers 10d10 captured slaver ships, and within two or three centuries a world is strip-mined, emptied of life, and drained of anything useful. Drones may enslave intelligent races for a time, letting them hope for a bargain until control is total, and take prisoners to study for weaknesses.

Artificers prize drone weapons for study, though they stop working once removed.