n medium construct mindless 

Perception +9; darkvision

Skills Acrobatics +9, Athletics +10, Stealth +9

Str +3 Dex +4 Con +0 Int -5 Wis +2 Cha -5

AC  19; Fort +7, Ref +11, Will +9

HP 50; Immunities bleed, mental, poison, death effects, disease, doomed, drained, fatigued, healing, necromancy, nonlethal attacks, paralyzed, sickened, unconscious

Speed 25 feet

Melee [>] jaws +8 (agile, finesse), Damage 1d10+3 piercing plus necrophidic paralysis

Dance of Death [>>>] (enchantment, mental, occult, visual) The necrophidius sways, its serpentine form undulating and clattering in a hypnotic rhythm. Each creature that witnesses the dance must attempt a DC 18 Will save. Critical Success The creature is unaffected and is temporarily immune for 24 hours.Success The creature is unnerved by the swaying and becomes flat-footed until the end of the necrophidius's next turn.Failure The creature is distracted by the swaying, becoming stunned 1. After it recovers, it is flat-footed until the end of the necrophidius's next turn.Critical Failure As failure, but stunned 3.

Necrophidic Paralysis (incapacitation, occult, necromancy) A living creature bitten by a necrophidius must succeed at a DC 20 Fortitude save or become paralyzed. It can attempt a new save at the end of each of its turns, and the DC cumulatively decreases by 1 for each save attempted. A creature that succeeds at this save is temporarily immune to necrophidic paralysis for 24 hours.

Bestiary 2, page 180.