As Skerples and Arnold K have written, you should create threats that ‘attack every part of the character sheet.’ I think this is a solid concept to keep in mind when doing creature design, so I had a stab at it. None of these monsters deal direct HP damage, although they are far more dangerous and annoying for it. Enjoy!
Outsider / Mineral
Level 9 / Armour 15 / Morale 10 / Encountered 1
Attack: Invert Weight (Special) / Weight of Worlds (Special)
An extra-dimensional being. Formed from a spiny kernel of sentient hyperdense matter, which vaguely resembles a crowned head. Stones and other debris orbit the creature’s obscured form.
Accretion: each round, all nearby creatures must DEX save or lose the item in their lowest inventory slot. Lost items are drawn into the Tyrant’s orbit and crushed into their component parts. Each successful Accretion adds +1 to the Tyrant’s Armour defense.
Invert Weight: the Tyrant inverts the weight of an opponent, sending them tumbling into the sky. This effect lasts until the Tyrant is killed; allow 12 combat rounds before the character is considered lost forever in the sky. For each combat round a target spends falling skywards, the victim takes d10 damage when they finally fall to Urth.
Weight of Worlds: the Tyrant doubles the weight of an opponent and all gear they carry. The PC’s maximum Item Slots are halved, and the slot size of each item is doubled. This effect lasts until the Tyrant is killed.
Commentary: a teeth-grinding encounter that steals from you every turn and gets stronger as it does so. It can also nerf your carrying capacity or send you hurtling into the sky. Fun!
Level 2 / Armour 14 / Morale 3 / Encountered d6
Attack: Lipoinduction (+1 Flab)
Resembles a hairless, fleshy anteater. A Flabmonger’s bite triggers a bizarre overproduction of lipids, causing tumorous bags of malignant fat to sprout from the afflicted creature. Once their prey has become too fat to move, a Flabmonger will slowly begin to feed.
Lipoinduction: Biological creatures bitten by a Flabmonger must fill one item slot with Flab. Filling more than ten slots with Flab is fatal. Flab is cured at the rate of one slot per week.
Commentary: I had the idea for these ages ago and never got around to writing them up. I think creatures that deal Wounds directly are pretty interesting design territory, which I’ve barely begun to explore. I like the idea of finding a really fat guy desperately crawling away from a Flabmonger ambush.
Level 12 / Armour 20 / Morale 10 / Encountered 1
Attack: Lithifying Gaze (auto-hit, d6 DEX drain, +2 Armour)
A great grey serpent, cast from innumerable scales of living shale. In the stony hollows of its stalactite-fanged skull, twin baleful lanterns cast a metamorphic gaze upon the tender flesh of the world.
Lithifying Gaze: automatically hits a target in line of sight. Target loses d6 DEX and gains +2 Armour per round; must break line of sight to stop the attack. Both effects fade at the rate of one point per day. An Occulith is immune to its own gaze.
Surprise: the Occulith appears to be inanimate stone until it moves, and always surprises unless the PCs are informed of its exact location.
Commentary: the ‘classic Basilisk’ given a slight coat of paint. The auto-hit is to stop the Occulith raising a target’s armour score so high that the creature can no longer harm them. You really want to find ways of blinding it or blocking line of sight while you escape. This is definitely a boss encounter and should be telegraphed as such.
Hypergeometric / Outsider
Level 5 / Armour 12 / Morale 10 / Encountered 1
Attack: Entropic Touch (d3 Max HP reduction + Armour damage)
Cursed revenants, the remains of those who thought to master entropy and instead became her servants. All things wither at their touch, ageing centuries beneath the Wight’s sour grasp.
Entropic Touch: targets struck by the Wight lose d3 maximum HP, and lose d3 points of Armour Defense if they are wearing armour. Hit Points lost in this way are never regained, nor can armour eroded by the Wight be repaired. Melee weapons which strike the Wight lose one dice size of damage permenantly.
Commentary: more item destruction, this time accompanied by permanent HP loss. PCs are going to really, really want to keep their distance from this thing. I would heavily telegraph its powers by describing plants withering and metal rusting around it, etc.
Level 6 / Armour 16 / Morale 7 / Encountered 1
Attack: Banish (Special Grab) / Summon (Special)
The Titan AIs were charged with preserving human life wherever possible. The Banishers were an attempt at creating non-lethal security synths. They take the shape of enormous six-fingered hands, which grasp intruders and evict them using teleportation loci embedded in their palms.
Non-lethal: Banishers are forbidden from killing sentient life. They will first ask you to leave the vault, and lecture you about trespassing.
Banish: the Banisher grabs an intruder and teleports them to a designated eviction zone. Traditionally this is the entrance to the vault, although sometimes more punitive locations are chosen.
Summon: truly vexed Banishers, when faced with repeat offenders, may teleport in other creatures from the vault to deal with you permanently. Roll on the encounter table for this floor. The summoned creature is not loyal to the Banisher.
Commentary: the Wallmaster from Zelda. I used to fear those things beyond description when I was a kid. Creatures that mess around with party composition and positioning are another under-explored niche in the bestiary.
Level 3 / Armour 12 / Morale Never Flees / Encountered d4
Attack: Dessicate (Special)
Slow-moving fibrous colony organism, resembling a tangle of hairy glass ropes. Driven by a mindless unquenchable thirst. The Dessicator assails other living beings with a multitude of tiny needles and extracts their water with merciless efficiency.
Dessicate: a biological target loses the water in their body. After one hit, they are Deprived due to thirst. After two hits, they lose d6 CON as the water in their organs is extracted. A third hit is lethal. Additionally, the Dessicator drinks one ration of water from target’s inventory per hit.
Slow: the Dessicator always loses initiative and cannot surprise.
Commentary: considering how important a resource fresh water is in Vaarn, I’m not sure why it took so long to create a creature that steals your water. These are annoying creatures but something PCs will probably learn to just run away from.