Black Dragons are described in the Monster Manual as creatures who “loathe seeing the weak prosper and revel in the collapse of humanoid kingdoms. They make their homes in fetid swamps and crumbling ruins where kingdoms once stood.”
The Monster Manual describes Will-o’-wisps as “malevolent, wispy balls of light that haunt lonely places and battlefields, bound by dark fate or dark magic to feed on fear and despair.”
Pixies are described in the Monster Manual as “standing barely a foot tall and resembling diminutive elves with gossamer wings like those of dragonflies or butterflies, bright as the clear dawn and as luminous as the full moonrise.
The Monster Manual describes Rocs as huge beasts with “wingspans that spread two hundred feet or more. At rest, perched upon the mountain peaks that are its home, this monstrous bird rivals even the oldest dragons in size.”
The Kappa is often described as a “child-sized fey being, resembling a humanoid turtle. They have a powerful beak and a head of thin, wiry hair lining an indentation in the skull roof, which holds a pool of water. This pool on top of the kappa's head is sometimes regarded as the source of a kappa's supposed mystical powers.”