Behold my first creature contribution (inspired by my need to add another creature to the Neutral Monster Incarnation Table for the induced reincarnation spell): a variation of the ophidian from the Monster Manual II (AD&D 1st Edition).
No. Enc.: 1d12 (6d8)
Movement: 90' (30')
Swim: 180' (60')
Armor Class: 6 (5 with shield)
Hit Dice: 3
Attacks: 1 (bite) or 2 (bite, weapon)
Damage: 1d4 + poison; or 1d4 + poison and by weapon type
Hoard Class: XVIII
Snakefolk are creatures of human intelligence who resemble large venomous snakes (average thickness 8-12") with two human-like arms that give them the capability of using tools and weapons. Their scales are the equivalent of scale armor. In combat, snakefolk attack by biting with their venomous fangs and striking with a weapon (if armed). Those who are bitten must save vs. poison or fall asleep for 4d6 hours. Upon waking, the victim must make another save vs. poison. Failure to save means the victim will gradually transform into one of the snakefolk within 1d4+3 days. The spell neutralize poison will prevent the transformation if used before it is complete. The spell cure disease will reverse the effects of the poison. Humans, demi-humans, and humanoids who fall unconscious from the effects of the poison will not be harmed, but will be bound and taken to special chambers deep within the lair until they are fully transformed. Enemies who do not fall unconscious or who resist the transformative effects of the poison are slain and devoured.
Snakefolk who use weapons are typically armed with spear and shield, sword and shield, trident, or bow. Snakefolk are equally at home in caves, trees, rivers, marshes, and deserts, and their coloration varies depending on the habitat of their colony. Those encountered in the natural habitat of their colony are able to surprise enemies or prey with a surprise check of 1-4 on 1d6 due to their camouflage.