As grodog mentioned at his blog, I'm hip-deep in keying out the dungeon level of Twisting Stair #1 for use in my home campaign (and for a prospective Roll20 online campaign). It's coming along nicely, although not quite finished in a shareable state.
One thing I like about the Twisting Stair zine is how it drops a tidbit without fleshing out the details. I find it just enough to jump start my creative process while leaving me completely free to follow my imagination. One example of this was the "Cultists of Yox" found on the Wandering Pairings random encounter table.
As a little teaser of what turned out to be a major faction in my adaption of the 1st level Twisting Stair dungeon map, here my take on the Cult of Yox.
CULTISTS OF YOX (New Monster)
Frequency: Very Rare
No encountered: 5d6
Size: Medium
Move: 60 ft plus, 60 ft leap
Armour class: 7
Hit Dice: 1d6 HP
Attacks: 1
Damage: By Weapon
Special Attacks: Jump, Climb Walls, Acid Spittle
Special Defences: None
Magic Resistance: Standard
Lair Probability: 80%
Intelligence: Average to Very
Alignment: Chaotic Evil
Cultists of Yox are 0-level worshipers of the aforementioned Yox (also known as Magog on some planes), a unique locust-demon of middling power. Yox/Magog is rumored imprisoned on a prime material plane, the exact plane a matter of conjecture for sages.
Most worshipers appear as normal humans, albeit chaotic and evil. If on the same plane of existence as Yox, 0-level cultists gain the ability to jump as per the spell (if not on the same plane this ability is not gained until reaching a full hit die). Long years of demonic worship, ingathering of additional cultists, and offering of sacrifices slowly transforms the devotee through molting into something more; the first molting raises the worshiper to a full hit die, and each successive molt increases its hit die by one and grants additional powers. As moltings make non-clerical spellcasting difficult, magic-using cultists do not molt or gain powers as described below (although some research spells which mimic these states for a time).
For every 6 cultists, there is a 1 HD sub-leader who's undergone a single molt, gaining a semi-hard segmented layer of chitin over their bodies (improving AC by 1 while still allowing armor use), small barbs protruding from their hands and feet, and very slightly bulging eyes. Due to their barbs sub-leaders can crawl on walls if on all fours as per a spider climb, although not on ceilings (and their hands aren't sticky). At this stage it is still possible to pass amongst regular people if concealing clothing is worn. Additional sacrifices and cultic energy from larger ceremonies (through successful proselytization) causes further moltings.
for ever 12 cultists there will be a 2 HD leader gaining a +2 to its AC (armor may still be worn) as its chitin further hardens. The leader also gains locust-like mouth parts which can chew through any non-metal. Materials as tough as leather or rope can be chewed through in 2-4 rounds, or softened by spitting a foul brown acidic spittle over the area against which the item must save against acid or be reduced to the strength of cloth. (Cloth can be chewed through in a single round.) A leader can also spit as a grenade-like missile attack (range 1/2/3) doing 1d6 damage. The target gets a saving throw vs paralyzation to avoid, and if failed item saving throws may apply at DM discretion.
For every 18 cultists will be an underpriest of between 3rd and 5th level spell casting ability. This priest will have gained a completely locust-like head, infravision out of 60', and grown an additional pair of locust hind legs. This allows triple-strength jumping as per spell.
There are rumors of more powerful priests in the cult than these, but this is unconfirmed.