Beast of the Week: Horned Serpent

Yesterday being Thanksgiving (I'm American if you didn't know), I was thinking of doing another monster from my traveling pocket notebook, based on the "turducken" (a duck stuffed in a chicken stuffed in a turkey and baked), sort of a "kill this monster, then a smaller one pops out of it, and when it's dead a third monster pops out" but that was just too involved. 

Instead, how about going back to Native American mythology and writing up another NA monster? 

Horned Serpent*
AC: 0 (20)
HD: 6**
Move: 120 (40)
Attacks: 1 horn, 1 bite or breath
Damage: 1d10/2d6+poison
No. Appearing: 1d4 (1d6)
Save As: F6
Morale: 8
Treasure Type: D
Alignment: Chaotic
XP: 725

Horned serpents are 50' long giant snakes with iridescent scales and one or two crystalline antlers protruding from their heads.  They live in lakes and rivers and may attack those that stray too close to their underwater lairs.  A horned serpent's bite is poisonous; those bitten must Save vs. Poison or die in 1d6 Turns.  Instead of biting, the serpent may spray poison in a 15' diameter cloud around it.  All within the cloud must Save vs. Poison or become sickened, suffering a -4 penalty to attacks and saves, for 1d4 hours.  The horned serpent can also use its horns to lure creatures near it.  Three times per day, the serpent can send out a signal.  Creatures within 120' must Save vs. Spells or approach the serpent and stand enraptured by the call for 1d4 Rounds.  The antlers of horned serpents are prized by Magic-Users and alchemists, and each horn can fetch 2d4 x100gp.