Why always sets of five monsters? Why not.
The Hind of Lamarand
There once was a king in the land of Lamarand who lived to hunt, and he was quite proficient at it. Before his first tooth had fallen out he had slain his first boar, and on the eve of his coronation his first lion. By the time he could grow a full beard these prey to him seemed paltry.
After that, the only hunt that could lift the king's ennui was the hunt of his fellow men. He enacted brutal taxation to push his people into poaching and other crimes as a pretense for this hunt and terrible execution. He had the royal woods re-modeled to make them inescapable mazes for intelligent prey.
Eventually the gods themselves took notice of the king's cruelty and corruption, and cursed him with a beastly form to match his soul. Furthermore, it's said they promised a great blessing to whoever took the accursed king's head.
But this is a vicious and toothsome lie. There was no curse, no sudden comeuppance for a lifetime of wickedness. The king demanded this transformation from his chief sorcerer himself, tired of the affairs of court and family. He intends to stalk and kill and gorge joyously until the end of days, the rumour of divine reward for his slaying a lure for the righteous and the foolish.
As the Hind the former king resembles a huge six-legged stag, fur shaggy and grey. From his lower jaw to the bottom of his sternum a fang-filled maw gapes. His eyes are still human, piercing-blue and full of predatory malice. He brings his hunting ground with him. For three miles around him a dense forest sprouts - and any corpses buried in the earth are lifted up with the sprouting trees, impaled upon their branches - and this forest crumbles behind him into rich rot as he prowls.
HD: 10 + Heart of the Forest
AC: As chain, reflects spells 3-in-6
Move: Twice as fast as a horse
Attack: 1d6 stomp/1d6 stomp/1d12 bite + swallow
Heart of the Forest: Whichever hex the Hind is in becomes a forest. If the Hind is killed within this forest, he will be reborn at the next full moon. Killing him outside the forest, or destroying enough of the forest before, after, or during killing him, prevents this.
Swallow: Targets hit by the Hind's bite attack must save or be dragged into its gullet. After that, they take an automatic 1d6 damage per round. They may cut their way out by dealing 10 damage to the Hind, but can only use light weapons.
A toddler-sized beastie with a face like a stepped-on rat and hooked, crooked claws at the tips of its gangly aye-aye fingers. Its fur is a patchy pale pink, and mucusy-slick like it's been sneezed on all over.
The first encountered stokey-pokeys were a breeding pair brought back from an expedition to the far west by the famed explorer Cosdenada, who claimed they were a gift given to him by the emperor of a golden land of the ever-young. As these creatures possessed a wondrous ability to aid one's power of recollection, they became an immediate fad among the elderly, scholarly, and occult. That sole breeding pair's children were carted off to many distant courts, and then those children were forced to breed to fulfill the clamouring demand for more stokey-pokeys, and so on and so on until the entire species' stock was horrifically inbred, and more likely to lobotomize you than help you remember something.
The fad for stokey-pokeys shortly thereafter died out, their original form and function surviving only in marginalia doodles. Feral populations, descendants of escaped and discarded specimens, survive in the overlooked places of the world, as the pets of addle-brained wizards and as especially-loathed pests.
AC: As chain (quick & tricksy)
Move: As monkey
Attack: 1d4 + Brainpluck
Brainpluck: The stokey-pokey reaches its long, clawed finger way up your nose and yanks out a piece of your brain. This does equal damage to your HP and to your Intelligence stat. If you've forgotten or overlooked something important (a clue, a secret door, etc.) then the damage to both is doubled, and the stokey-pokey retrieves a "remembrance pearl" - a hard, gristly wad of your own grey matter - and runs off with it. Eating the remembrance pearl will remind you of whatever it is you forgot. Covering your face completely prevents a stokey-pokey from brainplucking you. If a stokey-pokey misses with its brainpluck, it still gets its finger up your nose, but instead of picking its way into your brain it instead snags a booger so big you're astounded you could've missed it up there.
Named not for its commonality but for the peculiar effect it has on the human mind - though it appears quite monstrous indeed, it can mislead people into thinking it is an ordinary person who has been with them all along.
Without the veil of its deception, a croach can be seen to be a fleshy, conical body, like a human's head and armless torso with a sheet of skin stretched over it, terminating in a chaotic mass of legs branching off from its hips and each other.
Studying into the origin of the croach carries a similar effect. Researches conclude that croaches must be their second cousins, or neighbours they politely ignore.
AC: As leather
Move: As horse
Attack: 1d8 Kick + save vs. strength or be knocked back 10 ft. & prone, or grapple and carry off with strength 15
Commonplace Encroachment: A commonplace croach ambushes on a 5-in-6. If this ambush is successful, the croach insinuates itself into the party. The DM shouldn't outright say that there is a new member of the party, but imply so and reveal it if the party does a headcount or somesuch. For its part the croach will wait for or create an opportunity that allows it to isolate another member of the party and then brutalize them. Having a dog in the party reduces this chance to a 3-in-6. Having a bird or cat in the party nullifies the chance entirely.
A plague upon the Rivenlands, that lush territory where human expansion is limited by the unearthed ordinances of a thousand years of war. Perhaps the trenchmaul is one of those ordinances, or perhaps it's just a natural creature that adapted to the deadly front.
The trenchmaul is a beast with several bodies. The most important of these is its feeding body - a man-sized lump that resembles a meaty sweet potato with a four-lobed mouth on its side, most often buried 10 feet or so underground. Its other bodies - its hunting bodies - are dog-sized things between a lobster and a cricket, with broad and shovel-like claws. These are connected to the feeding body by tough intestinal/neural tubes.
Hunting bodies will attack moving animals, and assume motionless animals are dead and drag them underground to the feeding body. An encountered trenchmaul with have 2d4 hunting bodies.
AC: As unarmoured
Attack: Bite 1d8
AC: As leather, connective tube has AC as plate and 1 HP, if severed then hunting body dies a round later.
Move: As walking man while digging, as running man above ground
Attack: 1d6 snip or Drag Down
Morale: 6, 10 in defense of feeding body
Drag Down: If attacking a target from below, a trenchmaul will attempt to partially drag it down into the dirt. Win opposed strength test vs. strength 12 or be dragged into the dirt down to your knees. After that you're immobilized until you spend a full round making another opposed strength test vs. strength 12 or your pals help pull you out.
A fey gentleman with perfectly-coifed red-and-white hair and goatee, dressed in a green cape with brooches fixed with feathers and fur.
He fancies himself the justice for those outside the law: for the penned and hunted beasts and birds on which humanity feasts. When encountered he'll observe from a distance or question the party to suss out their eating habits. Vegetarians get his respect.
Those who've killed animals are made to stand trial and suffer the hunt from the preys' perspective. If they can argue that they showed respect to their prey they'll receive similar consideration - a head start or somesuch.
If bested, the todlowery will owe a boon, such as posing the same test to a rival party or revealing the location of treasure hidden in the forest.
HD: 4, or as animal form
AC: As leather, or as animal form
Move: As man, or as animal form
Attack: As weapon (typically a rapier or woodsman's axe) or as animal form, or Predatory Polymorph
Predatory Polymorph: The todlowery's preferred method of attack is to transform his targets into prey animals, and himself into their predator. When targeting a group, only the target with the highest save makes a roll - if they pass then so does the whole group, if not then they're all transformed. The todlowery must transform with them. The transformation lasts until sunset or sunrise, or until he's defeated or soundly escaped from.
Some example predator/prey pairings are as follows:
1. Fox & chickens
2. Weasel & rats
3. Dog & hares
4. Cat & sparrows
5. Eagle & monkeys
6. Bear & deer