Oozes are described in the Monster Manual as creatures that “thrive in the dark, shunning areas of bright light and extreme temperatures. They flow through the damp underground, feeding on any creature or object that can be dissolved, slinking along the ground, dripping from walls and ceilings, spreading across the edges of underground pools, and squeezing through cracks. The first warning an adventurer receives of an ooze’s presence is often the searing pain of its acidic touch.”
Trolls are described in the Monster Manual as “fearsome green-skinned giants, eating anything they can catch and devour. Only acid and fire can arrest the regenerative properties of a troll’s flesh."
Mimics are described in the Monster Manual as “shapeshifting predators able to take on the form of inanimate objects to lure creatures to their doom. In dungeons, these cunning creatures most often take the form of doors and chests, having learned that such forms attract a steady stream of prey.”
Flumphs are described in the Monster Manual as creatures who “mysteriously drift through the Underdark, propelled through the air by the jets whose sound gives them their name. A flumph glows faintly, reflecting its moods in its color. Soft pink means it is amused, deep blue is sadness, green expresses curiosity, and crimson is anger."
Doppelgangers are described in the Monster Manual as “devious shapeshifters that take on the appearance of other humanoids, throwing off pursuit or luring victims to their doom with misdirection and disguise. Few creatures spread fear, suspicion, and deceit better than doppelgangers. Found in every land and culture, they can take on the guise of any individual of any race.”
Succubi and Incubi are described in the Monster Manual as “inhabiting all of the Lower Planes, the lascivious dark-winged fiends can be found in service to devils, demons, night hags, rakshasas, and yugoloths. Asmodeus, ruler of the Nine Hells, uses these fiends to tempt mortals to perform evil acts. The demon lord Graz’zt keeps succubi and incubi as advisers and consorts."
Green Hags are described in the Monster Manual as “wretched and hateful creatures that dwell in dying forests, lonely swamps, and misty moors, making their homes in caves. Green hags love to manipulate other creatures into doing their bidding, masking their intentions behind layers of deception. They lure victims to them by mimicking voices calling out for help, or drive unwanted visitors away by imitating the cries of fierce beasts.”
Werewolves are described in the Monster Manual as “savage predators. In its humanoid form, a werewolf has heightened senses, a fiery temper, and a tendency to eat rare meat. Its wolf form is a fearsome predator, but its hybrid form is more terrifying by far — a furred and well-muscled humanoid body topped by a ravening wolf’s head. A werewolf can wield weapons in hybrid form, though it prefers to tear foes apart with its powerful claws and bite.”
Goblins are described in the Monster Manual as “small, black-hearted, selfish humanoids that lair in caves, abandoned mines, despoiled dungeons, and other dismal settings. Individually weak, goblins gather in large—sometimes overwhelming—numbers. They crave power and regularly abuse whatever authority they obtain.”
Banshees are described in the Monster Manual as “the undead remnants of elves who, blessed with great beauty, failed to use their gift to bring joy to the world. Instead, they used their beauty to corrupt and control others. Elves afflicted by the banshee’s curse experience know no gladness, feeling only distress in the presence of the living. As the curse takes its toll, their minds and bodies decay until death completes their transformation into undead monsters.”