Planar Bestiary
As fey spirits, coal nixies do not require air, food, drink, or sleep.
At about 3 feet tall, these coal-dark beings resemble spindly dwarves always surrounded by a cloud of swirling, choking coal dust. At need, they can briefly become a dangerous, spinning cloud of coal dust themselves. Clutching a war pick in one hand and laden with bags of coal, these bearded fey are brooding, perennial miners. They like to claim underground coal fields for themselves, and are jealous of others, wherever they might be, who try to claim coal for their own.
Coal nixies are of the Feywild, where coal beds are shot through with refulgent seams. They sometimes follow those seams to various worlds of the Material Plane, where other coal nixies have yet to make a claim. In such worlds, they spy on dwarves, orcs, and other creatures that mine underground, sometimes allying with them, but eventually betraying any trust they've built up.
Motive: Mining, claiming new coal fields
Environment: Any underground location in the multiverse, prospecting alone or in a group of four to six
Health: 12
Damage Inflicted: Moderate wound (4 points)
Movement: Short; short when climbing
Modifications: Speed defense as level 4 due to size; deception, perception, and stealth as level 5
Combat: A cloud of swirling, magical coal dust surrounds the coal nix. Creatures within immediate range that fail a Might defense task breathe in too much coal dust and violently choke. A choking creature can do nothing but loudly hack and cough on their turn, and attempt a Might task as their action to end the effect. Once recovered, defense tasks against the cloud are eased for one day. Additional precautions, such as wetting a cloth and breathing through that, provide an asset to defense tasks against the cloud.
A coal nix attacks with their war pick, preferentially targeting those overcome by their coal dust.
A coal nix can collapse into a whirlwind of spinning coal dust once every few rounds. All creatures in immediate range that fail a Speed defense task take 5 points of damage and are blinded; those who succeed still take 1 point of damage but retain their sight. While collapsed, the coal nix can move through spaces as narrow as 1 inch. The coal nix remains a whirlwind until their next turn; nonmagical attacks against the whirlwind have no effect.
Interaction: The coal nix's covetous ways mix with their often-sinister goals so that in some circles, they are thought of as creatures that help people find coal and other valuable minerals beneath the earth. A coal nix may indeed offer to lead prospectors to just such a find, but if not closely watched, leads them astray, or directly into a dangerous situation or trap.
Use: A group of territorial coal nix prospectors find the explorers who recently sold or used gems to make a purchase, asking questions about that gem's provenance.
Loot: Coal nixies may carry maps of coal seams that transcend planar boundaries.
GM Intrusion: The coal nix strikes a tunnel, wall, or ceiling, causing it to collapse on a character, inflicting damage and trapping them beneath the rubble until they can escape.