Another type of creature that has come from the other plane

An aberration that can be found in the depths below Hawjio

In the darkness you notice a point of light erupt no bigger than a candle, quickly followed by several dozen more and a soft metallic sound, like a man at the dinner table sharpening his knife against a fork.

Not everyone who gums up the courage and a weapon who delves a dungeon survives to become a hero, or dies to be avenged or memorialized. There are a number of poor souls who find the third path, becoming the cursed.

What if there are good or neutral aligned dungeons that dont want to use goblinoids for their stock mobs? 

Aha, the canid kobold to the rescue

One of the Four Divine Guardians, Beast God Antihero exists to hunt, defeat, and consume would be heroes. It steals power from those it slaughters and consumes. 

Mythical creatures associated with Terrasquestone

Carcohl is only known of through mnemaglyphs found in the deepest portions of the Gygaxian Gyre. If the scratchings in the walls can be believed, Carcohl or The Carcohl is a dragon snail of Gargantuan size

A Geezer (proper noun) is the male version of a Hag. They are not related to, nor do they interact with Hags.

Orthran are rare encounters in the Gygaxian Gyre, and are accorded a status of being a dungeon cryptid.

Sure, sure, mate, you're seen one, and slew it, and magically survived to come back and tell us about it. You're a con and a swindler but your story was at least entertaining.

A monstrous race encountered in the depths of the Gygaxian Gyre, beneath Tarrasquestone

also known as a great rat, wererat, or goblin rat

also known as an eye-pillion, dungeon sneak, or the most common Eye Spider

Also known as the Daughters of Parmak, the Burning Ones, Maidens of the Skull, and other colorful terms. They are once mortal magic using women who have become twisted, evil, and undead.

"AAAAAAHH, it's a troll!"
"Protect the women and children! Grab your torches!"

"AAAAAAHH, it's a troll!"
"****head... we banned him five times and he keeps making new accounts about how he pwns all and that he>>>>>>>>>>>>>>>>>>>j00!"

A parasitic mold with an unusual lifecycle and powerful mind-control properties.

A vile an insidious pest

They appear to be very dark, overly large worms - perhaps a handspan in length and half as thick as a finger. That and their matt, dull skin marks them as something other than a typical earthworm.

'I stand before you now to tell you that the gods have spoken to me! Obey not the strictures of the Church! They seek only to deprive us of the very same pleasures that they enjoy themselves'.

Known fully as 'Nind Vel'uss Tahcaluss whol nind ehmtu siltrin' or 'They Who Hunger for Their Own Flesh'