For the sake of completion, here are the rest of my personal notes for certain monsters in my own setting.
Nightshade: These will be unique creatures of great power, forming a kind of Umbral pantheon of dread demigods.
Nightcrawler: Resembles a hooded serpent and is called Erebus.
Nightrunner: Resembles a great hound and is called Tolfand.
Nightstalker: Resembles a tall, but not giant, hooded and cloaked human and is called Malvikar. Beneath the cloak is the swarm of beetles that is Khefra.
Nightswarm: Disguised as the nightstalker, Khefra manifests as a swarm of black scarab beetles that normally shapes itself into a humanoid form. Khefra represents an entire lost pantheon of gods, of which the other nightshades are revived examples - but Khefra may re-absorb any of them at will. May act as a cohesive figure, a disparate swarm, or some of both.
Nightwalker: Resembles a bearded titan and is called Chernobog.
Nightwing: Resembles an enormous bat and is called Camazotz.
Ogre: Often ruled by oni (ogre magi) or by hags. Ogres are also known for hurling live giant beetles in combat. Ogre with horned helm that gains gore attack as minotaur.
Ogre, Rime: Slightly more massive ogre with frost giant blood.
Ogre, Salt: Not actually an ogre at all, but a kind of cursed elemental of water and mineral trapped in a form about the size and shape of an ogre. Inflicts Constitution damage by absorbing moisture from living creatures.
Ooze: Sometimes used as siege missiles.
Otyugh: When slain, this foul monster deliquesces into some form of ooze - possibly chosen at random.
Owl, Bandit: An otherwise ordinary bird with dark raccoon-like markings across the face and a penchant for filching small valuables. Known to work in pairs or small groups.
Pegasus: Give the creature an air elemental quality and the ability to assume Gaseous Form (with a rider).
Red Putty: A type of ooze that resembles red clay. Drains blood on a successful hit.
Rust Monster: Have some kind of primitive race or society wearing armor made from the hides of rust monsters that affect metal items striking the armor as a living rust monster. The primitives have no metal items themselves.
Salamander, Storm: Violet and silver, with a serpentine body and four legs. Flies. Crackles with electricity. Very fast when striking, Immune to damage from electrical attacks.
Snake, Singing: An otherwise ordinary reptile that can imitate most forms of singing, from birds to people. Uses this ability to attract prey - typically birds.
Snake, Snapping: This large serpent has scales similar to the shell of a turtle and powerful jaws that deliver a crushing bite. It is very aggressive and also poisonous.
Sphinx: Respected keepers of knowledge and ancient wisdom, sphinxes were once coveted by great rulers as viziers and advisors. Monsters categorized as sphinxes include: Lamia (fallen sphinx - without wings), Lammasu (greater sphinx), Manticore (degenerate), and Shedu (high sphinx).
Spider, Tarantella: Venom may be collected and used as poison.
Thoul: Posing as a hobgoblin king and rises as a ghoul lord if slain. Possibly a personal guard of slightly weaker thouls posing as hobgoblins.
Toad, Javelin: This giant toad has a piercing bone spike at the end of its long tongue that it uses to impale prey.
Treant, Baobab: Ancient and enormous specimens possessed of incredible strength and near-infinite patience.
Treant, Tainted: A treant that has absorbed some sort of poison through its roots and become almost diseased in the process. This creature is twisted and evil, seeking to pass the taint on to any living creature it encounters.
Troglodyte, Primordial: A gigantic, barely intelligent specimen of troglodyte intended as a singular monster to be found in a "lost world" area in much the same role as King Kong.
Troll, Black: Bred by a black dragon for use as minions, this type of troll is shorter and broader than the standard troll and is immune to acid. AC: 3, HD: 5, Dam: 1d4/1d4/1d8, Save: F5. Regenerate 2 HP/round after 2 rounds. Excellent swimmers.
Unicorn: Unique specimen or group that are vampire hunters and slayers - impaling their victims with their horns.
Unithorn: Plant-based unicorn-like creature.
Voraile: Like a giant wasp built on the same lines as a cheetah, this fast and agile creature possesses powerful jaws and a long tail tipped with a vicious stinger. The spotted carapace is hairless and small insect wings allow incredible leaps, but not true flight. The creature's six legs are each tipped with vicious retractable claws.
Wasp, Ordinary: Certain kinds of humanoids will hurl or drop wasp nests in combat.
Weredead: Undead lycanthropes, including ghoul wererats and wight werewolves.
Wereogre: An ogre lycanthrope with a cave bear wereform.
Wraith, Marsh: Has poisonous marsh vapors in its makeup. Often accompanied by a will o' wisp.
Wyrwurm: A giant draconic snake with wings - and no legs. Venomous bite and spitting breath weapon where the poison is also imbued with the properties of the breath weapon. Less intelligent than dragons and no spellcasting.
Yellow Mold: Can be found on mindless undead or constructs - offering a double threat. Sometimes growing on the back of a stuck door or the inside of a chest lid. Also on the walls and floor of a pit. Some creatures even cover missiles with yellow mold to fire at enemies. Will often ignore disturbance from non-living creatures and is encouraged to grow within crypts and tombs for this reason. Any site with "Golden" in the name might actually refer to a profusion of yellow mold. "The walls, floor, and ceiling of the great central chamber are completely covered in gold!" *snicker*
Zombie: Excellent means of carrying growths of yellow mold, green slime, or other hazard. Some necromancers create their zombies specifically for this purpose.