The Necrophidius

Back to some conversions whilst I finish my Cthulhu Mythos notes - first up "The Necrophidius".

The necrophidius, called the "death worm" by some, is an artificial creature, built and animated by a wizard or priest for a single task, such as protecting a particular treasure or assassinating a specific target.

The necrophidius resembles a bleached-white skeleton of a giant snake, topped by a fanged human skull with constantly whirling, milk-white eyes. The death worm's bones are warm to thetouch. The necrophidius is nearly undetectable to most senses. It is absolutely silent; it may open a door and cause the hinges to creak, but it makes no noise whatsoever even when slithering across a floor strewn with leaves. The necrophidius has no odor. The necrophidius keeps up a constant motion, moving with a macabre grace.

NO. ENCOUNTERED: 1
SIZE: Large
HD: 2
MOVE: 30 ft
AC: 18
ATTACKS: 1 (Bite) 1D8
SPECIAL: Eye Magic, Darkvision 60 ft, Anti-Magic
SAVES: M
INT: Average (Human) Intelligence
ALIGNMENT: Neutral
TYPE: Aberration
TREASURE: -
XP: 320

A necrophidius is created for a single purpose. It may be created in one of three ways.

The first is via a magical tome, akin to a manual of golems can provide secrets of the necrophidius's construction (the Necrophidicon, as it is sometimes called, must be burnt to ashes, which provides the animating force for the monster).

Alternatively, a wizard can create a necrophidius by his own means. This process is long and complex, and requires that the wizard be able to cast limited wish, geas, and charm person spells.

The third method enables a high-level priest of some Powers to build a necrophidius. Again, the method is long and tedious. It requires the spells geas, neutralize poison, prayer, silence, and command.

Whichever method is used, the monster requires the complete skeleton of a giant snake (either poisonous or constrictor) slain within 24 hours of the enchantment's commencement. The construction takes 500 gold pieces worth of herbs and ointments per hit point of the necrophidius; and ten days are required. 

A necrophidius is built for a specific purpose (which must be in the spellcaster's mind when he creates it), such as "Kill Ragnar the Bold" or "Keep the Scepter of Trystom safe on this altar."

The necrophidius has a reasonable intelligence, and does not seek to twist the intent of its maker, but its enchantments fade when its task is done or cannot be completed, for example, when it kills Ragnar, or when the owner decides to use the Scepter of Trystom. 

The crafter must want the necrophidius to serve its purpose. He could not, for example, build a death worm to "Sneak into the druids hut and steal his staff," if the crafter really intended for the necrophidius to merely provide a distraction. He could not build more than one death worm and assign each of them to kill Ragnar, since he could not imbue in the second death worm a task that he intended the first one to complete. For this reason, ne-crophidii are almost never seen working as a team. There are rumors, not well-founded, that there were once methods to make a necrophidius that conformed to all current specifications except that it gained 1 Hit Die every century it was pursuing its purpose.