Lock Lurker

It passes for a coin, a cold disk of copper or bronze (silver or gold 25% of the time), with folding legs underneath around a razor iris of teeth. Its stinger, up to a foot long and blindingly fast, normally sits on the Ethereal Plane, invisible from the Prime Material. Thieves pocket them as heavy coins until stung, and lurkers ride in purses to better hunting grounds. Its bite and sting are silent unless they hit metal.

The teeth cut hide, hair and leather but not metal. The stinger materializes only as it strikes, piercing any armor and and leaves anything below human size stunned for 1-2 rounds. Its venom slows the victim (as the spell) on the next round, when a saving throw is made. On a success the slow lasts one more round, then fades. On a failure the victim is paralyzed at once for 1d6 hours, every limb locked rigid so that moving them is hard and risks injury, followed by 1d2 rounds of slowness before full recovery. A lurker carries enough venom for 40+2d4 stings a day.

Venom and food are stored in stretchy sacs on the Ethereal Plane, shuttled across by unknown means. From the Prime Material, only a materialized stinger is a target; from the Ethereal, the whole creature is, unless it spends a round crossing fully over, which grants any ethereal foe a free attack. It moves body matter between planes regardless of physical or magical restraint but can never retreat wholly into the Ethereal. Its attacks and venom work the same on both planes, it has 60-foot normal vision and infravision on each, and it slowly regrows lost parts.

The name comes from its use as a guard on chests and doors, stinging intruders through keyholes. Assassins tuck them under pillows and inkwells or in boots so a paralyzed target can be killed without a sound.

Hermaphrodites, any two adults that meet mate and part, and each produces a sac of 1d12 x 10 eggs within 1-4 months, 60% fertile, which hatch untended in 1d6 weeks into 3d6 young. These eat the remaining eggs, and sometimes siblings, until they can travel, then scatter. Adults never fight each other, and they mature in seven years.

Escaped lurkers do not hunt so much as wait. Like some spiders they prefer settled areas, eating insects, rodents and similar pests. Their clear, gummy, seaweed-scented venom sells for about 10 gp a flask for use in inks, potions and slow-related processes. A mostly intact body, a favorite component in oil of etherealness, is worth 2 gp, or 6 gp with the stinger intact, and egg sacs fetch about 25 gp.