Planar Bestiary
In some worlds of the Material Plane, "unearthly fire" is understood to be dangerous levels of radiation.
Vesieds appear as oddly proportioned humanoids with disturbing facial features and bodies studded with implanted objects.
Normally dormant, vesieds are sometimes found frozen solid and immobile, covered in ice. Recently, some have been found in the glaciers of high mountains on many different worlds of the Material Plane and, according to one account, deep inside a cursed moon "crashing" from one plane to the next called the "Planebreaker."
A vesied left undisturbed in ice continues their trip down the ages. But too much vibration rouses them, and they unfreeze themself in a blast of unearthly fire.
Motive: Mysterious
Environment: Anywhere in the multiverse where it's cold, alone or in small groups of three to six
Health: 25
Damage Inflicted: Moderate wound (5 points)
Armor: 1
Movement: Short; short when swimming; immediate when hovering
Modifications: Might defense tasks as level 9; Intellect defense tasks as level 3; ancient lore and machine lore as level 6
Combat: A vesied's bite is vicious, inflicting a moderate wound (5 points) and, on a failed Might defense task, 2 additional points of bleeding damage each round or until the bleeding can be stanched with an action.
More worrisome is a vesied's ability to generate an unearthly fire attack once every few rounds, either as a long-range ray attack against a single target or as a burst that affects all creatures in immediate range. In both cases, the attack inflicts a moderate wound (5 points) (ignores Armor, except from force fields).
A vesied also has a way with automatons and machines, being partly machine themself. With a touch, a vesied can attempt to convince a machine or automaton to do their bidding for a few rounds.
A vesied is immune to cold attacks.
Interaction: If communication can be established, the average vesied is found to be a lonely castaway from an inexplicable past, interested in returning to the ice. However, they are curious about any news or clues leading to the location of a group called the "Erodel" that almost every vesied seems to viscerally hate for past crimes (crimes that make the vesied too angry to explicate). Usually, no one knows what they are talking about.
Use: As the PCs pass through the mountains, an avalanche shakes snow from a high pass, revealing a pocket of frozen vesieds.
Loot: Vesieds seem to be partly machine, and the body of one could be salvaged for a few cyphers such as a fireproofing crystal cube or a frigid wall cuff.
GM Intrusion: A character that takes damage from the vesied's unearthly fire attack suffers acute radiation sickness, a level 8 disease that drops them one step on the damage track for each day they fail a Might defense task until they expire or receive magical healing.