Tressym

A tressym is a house cat, usually gray, tabby or black, with two bat-shaped wings on its muscular shoulders. Coats vary as much as any cat's. Hollow bones divide the wing membrane into arcs like a bat's fingers, but the whole surface is feathered.

They stalk, pounce, claw and bite like any cat, and flight makes them deadly to birds and flying insects, though they spare eggs and nestlings. They aim for the eyes and learn from one fright: a tressym that sees a wizard's wand fire will mistrust humans holding sticks forever. Beyond 120-foot infravision, it senses invisible creatures and objects within 90 feet, identifies by smell, taste or touch anything lethal to the thinking races, and seems immune to all known poisons.

Tressym only breed in one northern district of a distant kingdom, lairing in a gorge and hunting farm fields day and night, but wild and tame strays roam all temperate lands. Locals feed them, tolerate their vandalism and screeching midair brawls, and forbid mass or magical trapping, valuing them as owl-grade mousers. They avoid dogs and cats rather than fight. They tolerate one another but rarely share lairs, ignore bats and griffons, and rally together against their hated foes, stirges and manticores. Some enjoy harmlessly teasing dogs.

Likely the leftovers of some ancient wizard's experiment, these semiwild cats live 20 years or more and fly away from harsh winters. They mate like ordinary cats, not for life, and crossbreed with wingless cats, though only 10% of those kittens are tressym. Bright enough to form deep loves and hatreds with humans and elves, they will even die for a friend.

Some mages have made them familiars. A tressym offers cat and owl senses, handles delicate objects as well as a thumbless paw allows, reports what it sees, stays on task despite instinct, and names poisons for its master, even harmless-seeming gases. It cannot pass on its immunity. It cannot lift even a halfling, but by beating hard it reduces a halfling's fall of 90 feet or more to 2d4 damage; heavier creatures get no help.