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.”
The Pokédex describes Gengar as “mean-spirited creatures that enjoy tormenting people, hurting them and overtaking them. They are most active during full moons, creeping out in the dead of night and disguising themselves as shadows.”
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.