Amphitere

Amphitere 
Supernatural animal CE Morale 7
AC +4
HD 2
MOV 6 ground 24 air
Att Constrict d6 or Bite d6+poison

Amphitere are flying bat winged snakes which can at times swarm in large colonies and are associated with evil and darkness. Big enough to constrict a person but not swallow an adult. Able to get into tight spaces and can fold wings well enough to crawl in drains. Their venom is fatal in one ten minute turn, but a slow poison spell or a skilled healer can treat a victim for an hour can keep them alive. They can hover around a person and snap at them or grapple then on following rounds either constrict each round for a d6 or bite them with a +2 to hit.

They can work in packs and will coordinate their attacks by instinct rather than design. They often guard locations sacred to darkness or exotic resources. Some live alone but groups even large swarms are not unheard of.  They hate Ibis and will avoid them due to some instinct. Some countries keep many Ibis and you can almost never see a Amphitere in such places

Some say they are spawn of the great serpent of darkness and chaos Apep enemy of the gods. Their attraction to places of evil, darkness and magic attest to this. They have been known to attack light sources and can see with heat sensors without light. They often are used as guards but don't actually accumulate or hoard wealth on their own.

1in6 are runts with only 1HD and do only d4 damage and poison only does a d4
1in6 shed wings yearly for several months usually in most inactive season
1in6 have venom that inflicts 2d6 necrotic damage the next round save for half
1in6 have a venom that with each failed save victim becomes weaker losing d4 stat points which take a hour per point to recover, at zero STR they fall unconscious
1in6 have venom that inflicts a HP damage per round until death if save fails
1in6 have acis venom that burns for a point a round for 2d4 rounds
1in6 have a poison that when the victim dies their bones then flesh liquefy
1in10 require silver, iron or magic weapons to hit
1in10 spit blinding venom range 2 instead of use poison
1in10 have venom that renders victim unconscious in a round and dead in a turn
1in10 are intelligent and 1in6 of those have clerical or wizard abilities with a d4 levels
1in20 can turn invisible for a turn every hour
1in20 can breath firebolt or lightning or frostbolt for a d6 damage with a range of 3
1in20 can produce a size 2 circle of darkness for a turn a day
1in20 are huge loners that eat their kin and have 4HD and have a d8 damage

Adventures
1 Several Amphitere have got loose in a house and need removal 
2 A merchant has discovered cinnamon trees on a island guarded by Amphitere 
3 Each night people are found dead and children and pets have vanished
4 A evil high priest rides a huge Amphitere surrounded by multiple small ones and terrorises locals from a old ruin
5 A farmer recently drove away an ibis colony and now the area rampant with Amphitere, go find some ibis, prices on pet ones have gone up
6 Witches have a formula to create them, find and stop them
7 A cult of the snake cult of darkness have been spreading these fiends
8 A swarm is led by a intelligent queen with spells stop her and stop the swarm
9 A wizard had a breeding pair in his menagerie that escapes, find and kill them
10 A healer wants to make a antivenom potion and needs a live specimen

A note on all the random roll for varient breeds
-you can just pick some or roll till you get something you like
-they are for when you get jaded or not surprised by common variety
-some mutualy complimentry or exclusive, you decide
-give you room to make them weaker or stronger