Here are some monstrosities out of my brain. All text here licensed CC-BY-NC-SA.
Not entirely organic, a furnace grizzly is a organism-made-machine that is in the form of a large bear but with a roaring furnace of a heart. It is a deforestation device; it devastates woodlands one tree at a time, reducing them to ash. To destroy, it must be dismantled or its fire quenched.
Optional Stats: 8 HD, AC 17, Move 40’, Attacks: Claw, Spurt Flame.
A mad wizard’s cross beween a narwhal and an axolotl. About the size of a house cat, they are pale white, have external gills like an axolotl, and a horn like a narwhal. They can only live in slightly warm water and need excellent oxygenation and nutritional balance to survive.
Narlotls are extremely rare and a trophy animal. They are trapped by hunters and sold for a high price. They are also revered by several cultures for their resemblance to angels, unicorns, mermaids, and the moon. Their organs are used in many traditional medicines, purporting various ameliorative effects.
Optional Stats: 1 HD, AC 10, Move 5’, Attacks: Toothless bite.
A terrible beast to behold: a shaggy fur coat and eight limbs ending wolverine claws. Living solitarily in nests deep in cold environments, these beasts are very territorial and have a keen sense of smell. They are apex preadators, hunting down anything big enough to not be utterly destroyed by their attacks.
Optional Stats: 8 HD, AC 18, Move 60’, Attacks: Bite, Claws.
A dragon that cannot stop flying else it dies. It has a metabolism and biology that demands near-constant feeding. It is a terrible menace to surrounding ecology and settlements.
They are said to come from biology principles run overexcited: some small fish can grow to the size of their containers. The same can be true of any creature; that given enough food and space, it can grow without bound. Prowler dragons are said to be the result of this principle applied to hummingbirds. As a result, every prowler is unique and depending on its habitat, of different size and form.
Varying stats.
A totally blind wyvern, navigating by tactile and olfactory cues. Nosers have olfactory glands in orifices around their body, and attempts to catalog the number of glands often are criticized as incomplete. Indeed, their sense of smell is so precise they often drop out of the windy upper atmosphere to grab prey with large claws.
Optional Stats: 8 HD, AC 15, Attacks: Claws, Bite.
A large, cicada-like insect that can seemingly reanimate the deceased. They chew through the skull between the eyebrows to implant themselves in the body’s brain, then taking neurological control and reviving the body. A flood of hormones and neurotransmitters from the bug stimulates the brain long enough to restart vital functions, given that the body is not too degraded.
The bug biologically integrates itself into the new host, which reanimates. The ghouls are typically aggressive and voracious, eating anything that moves. The only way to surely kill one is to destroy the embedded bug.
Varying stats depending on host.
These moths feed on humanoids’ saliva and injects them with a psychoactive compound that causes somnambulism for several weeks. The sleep is especially deep, and somnambulists can become violent if attempted to be woken.
The moths cannot handle prolonged sunlight exposure and live in dark places. They stay near their sources of nutrition, venturing forth at night to feed. Their wingspan is 12 feet and they can stand as tall as a large dog on the ground.
Optional Stats: 4 HD, AC 14, Move 60’, Attacks: Mandibles, Suck Saliva.
(Based on Slake Moths)
This is a flowering plant that hyponotizes and psychologically entraps those who spend too long looking at it. Some of simple mind are able to withdraw from its power, seeing only an unremarkable little flower. However, those who are often involved in deep and pensive thought find their mind racing, and become dually hypnotized by perceived beauty and their own thoughts.
Should those transfixed be able to withdraw, they find their minds expanded, and their mental processes more profound. However, should one come too close to the Rose, they will prick themselves on its poisonous thorns, and die soon after.
(Inspired by Greek mythological sirens and the Averns of Shadow of the Torturer.)
Leaf People are the source of half-seen motions deep in the forest, gardens, and other thickly green spaces. They are known well to druids, hermits, and those who spend much time in nature, whose only descriptions of them are as “being made of the forest itself.” They are said to whisper esoteric knowledge in the rustling of leaves, and the murmur of the wind.
Optional Stats: 3 HD, AC 13, Move 30’ in green areas, Attacks: Thorn.
(Inspired by the Green Man architectural motif.)
Tiny butterflies that can carry information from brain to brain. They float in through exposed cranial orifices to the brain, pollinate, then leave. Pollinators are too small to really make out what their form is, almost indistinguishable from oversized quickly-moving dust particles.
The overall effect on the pollinated is to transmit ideas, at the highest complexity the receiver can understand. If a large enough swarm of pollinators is present near enough exposed brains, they will become overwhelmed with a common thought. The resulting actions depend entirely on the transmitted thought. If a huge swarm is present, the affected group can achieve a hive-mind status.
No stats; too small to fight individually!