Shadow Lurker

It has the manta shape of an ordinary lurker but is only a dark, hazy silhouette creeping across ceilings and walls. In a gloomy dungeon it would be nearly invisible, except that every shadow cast by nearby light, the party's own included, bends toward it. Under a flickering torch, the one shadow that does not dance is probably the monster.

Slow, it waits for prey to pass below or beside it, then strikes 1-3 man-sized targets within 20 feet as a thick black mist fills the area for one round. It wraps them tightly, coating skin and clothes as if in thin black ink. Every round its numbing cold deals 2d4 damage and saps 1d2 Strength from each victim, dying when either Strength or hit points reach 0. A victim holding a weapon can strike back from inside if they first make a bend bars/lift gates roll to push against the constriction.

Attacking it from outside risks the prisoners. A weapon blow has a 75% chance of hitting a victim for full damage instead (choose randomly among several), since the creature pulls them into the way. Area attacks deal half damage to every victim, or a quarter on a successful save.

Sleep, charm, hold and cold do not affect it. Faerie fire and light have only their ordinary effects, but continual light paralyzes it for one round per caster level. Color spray instead deals it 2d6 damage without harming those inside. Clerics cannot turn it. Though slow, it can squeeze through any gap, and at 30% of its hit points or less it flies to the nearest crack or doorway to escape.

Shadow lurkers avoid one another except briefly after a split, sensing their kind hundreds of yards away and leaving any area another already claims. They can also sense shadows, which they hate and always attack within 50 feet. They seem to live only to feed and multiply, and whether they communicate at all is unknown, though unlikely. Stolen Strength is stored, and at 50 points the creature divides in two, the offspring leaving at once to find its own territory.

They kill any living thing and even some undead, such as shadows, but being slow and easy to spot, they mostly threaten the careless. Victims dissolve into shadow and are absorbed, leaving only their gear. A wish to restore an absorbed body produces only a hostile shadow in the dead person's likeness, which attacks immediately. They keep no treasure beyond this abandoned equipment, and when too much piles up to warn new prey, they move on.