Necrophidius [Golem]

Some call it the death worm: the bleached skeleton of a giant snake, capped by a fanged human skull whose milky eyes spin without pause. The bones are oddly warm. It is never still, gliding and coiling with eerie grace, yet it has no scent and makes no sound even crossing dry leaves, though a door it opens may still creak.

It loves ambush; its silence imposes a -2 penalty on opponents' surprise rolls. If not surprised itself, it performs its Dance of Death, a mesmerizing sway laced with small magical flickers. Onlookers who fail a save vs. spell stand frozen as if under hypnotism while it slides in.

The bite deals 1d8 damage and forces another save vs. spell; failure means 1d4 turns of unconscious paralysis. This is magic, not venom, so dispel magic ends it while neutralize poison is useless.

Its intelligence is a magical imitation with no real mind behind it, so sleep, cause fear and other mind-influencing spells fail. Poison cannot touch it, and it never sleeps or eats. Despite appearances it is not undead and cannot be turned.

Each one is built for a single job, such as guarding a treasure or killing one person. One route relies on a rare book comparable to a manual of golems; the book is burned and its ashes animate the creature. A wizard may instead devise the process himself, a long effort that requires him to cast geas, charm person and limited wish. High-level priests of some powers can manage it too, using snake charm, silence, prayer, quest and neutralize poison. Every route needs a complete giant snake skeleton, constrictor or venomous, the snake killed no more than a day before the enchanting begins, plus ten days and herbal salves and unguents costing 500 gp for every hit point.

The task must be in the maker's mind as he works, perhaps slaying a certain knight or keeping a certain scepter on its altar. The construct does not twist its orders, and its magic fades once the goal is met or becomes impossible, as when the knight dies or the owner takes up the scepter. The maker must truly want success: he cannot send one to steal a druid's staff if he only wants a diversion, nor give two worms the same killing, since he cannot sincerely intend both to do it. Hence they almost never work together.

Unreliable rumor tells of a lost variant that gained 1 Hit Die per century spent chasing its purpose.

It needs no food and serves no natural function, existing wholly outside the ecosystem around it.