Three Beasties

Toadiathan

HD 12  AC chain  Bite 2d8+swallow
Mov 9  Int 3  Mor 7
Wants food, sleep

<Inhale> 60' cone.  All humanoids and loose objects are sucked into the toadiathan's mouth, and it makes a free bite attack against all of them (complete with swallow chance).  Characters with a free hand and something to plausibly grab onto can make a Str check to avoid being sucked in.  Usable every 1d4 turns.

<Barf> If the toadiathan recently sucked in a bunch of stuff with its Inhale ability, it can barf it all back out again.  (In a swamp, assume it is always inhaling enough water to use this ability.)  All humanoids in a 60' cone are knocked prone to the edge of the cone.  Str check to hold onto held objects, with a +4 bonus if the object is held with two hands.

Toadiathans are capable of hibernating for long periods of time.  They usually  bury themselves in dirt when they do this.  They are mortal enemies of froghemoths, and the two titans will invariably fight to the death when they encounter each other.  Their flesh is both poisonous (3d4 damage across 3 minutes if a save is failed, or 1d4 if successful) and an antidote for other poisons (new save allowed for all other ongoing poisons).

Hungering Shadows

HD 4  AC none  Tendrils 1d6 cold (all adjacent targets)
Mov 12  Int 1  Mor 12
Wants darkness, murder

<Shadowstuff>  Double damage from light.  Normal damage from fire.  Immune to all other damage.

<Anathema>  Perishes instantly in bright light.  Torches don't phase it, but if it is faced with a large bonfire (burning pile of furniture, flaming wagon) it will retreat someplace safe, such as deeper into the dungeon or into a chest (possibly trapped).  Can be easily defeated if you successfully chase it down with a flaming wagon.

Looks like a slithering heap of shadows or flatworms, crowned with an inky black cow skull.

Moonchild

HD 6  AC chain  Scream 2d6 slashing, 120' range
Fly 12  Int 14  Mor 6
Wants books, clear weather for stargazing, to never be gazed upon

<Spells> Knows 2 spells from this list, each usable 1/day: sleep, command, telekinesis, chill metal, illusion, blindness.

<Don't Look At Me> To see a moonchild is to know them, and that is destructive to their moonflesh.  Essentially, every non-moonchild has a gaze attack that is usable only against moonchildren.  If you spend a whole turn looking at a moonchild, it takes 2d6 damage (or 1d6 damage if you spend only part of your turn).  Save negates (for brevity, consider making one save for all incoming damage).  Blind characters cannot damage a moonchild in this way, and characters with only one eye deal half damage.  Characters with more than two eyes deal proportionately more damage.

Towheaded child with oversized head and milky eyes.  When you look at them, wounds erupt under your gaze.

They are born from women who looked at the moon too much while pregnant.  (Just as mooncalves are born from cows that do the same.)