(agree with CR 1) ...so beginning with what was written in Tizun Thane and working up..
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Green gremlins are implike fey creatures that inhabit dark places such as ancient forests, caves or dungeons. They have a horrible visage with vampire-like fangs and drooling lips. Leathery-skinned, they have a wiry build with long limbs and large hands and feet, and are equally at home climbing across walls and ceilings as they are on the ground.
They collect and hoard any trinkets they can find, often in secret hidey-holes only accessible via climbing. Green gremlins are capricious and unpredictable; many are malevolent and ill-willed, though occasionally good-natured ones may be encountered. They are often solitary, though may work together in small groups for a time or associate with other creatures such as darklings or goblins.
I came up with the following, but suspect it might have got a bit too wordy:
A green gremlin is a capricious fey that inhabits dark places such as ancient forests, dungeons or derelict buildings. Long-limbed and leathery, these implike creatures have horrible faces resembling drooling, vampire-fanged goblins. Their large hands and feet are clawed and sticky, allowing these wiry beings to move across walls and ceilings as easily as the ground.
A green gremlin's bite causes supernatural terror: they love to bite someone and chase the terrified victim. While they prefer fighting with their claws and fangs, a green gremlin can also snatch up objects and wield them as improvised weapons: hurling a rock, stabbing with a sharpened bone or broken bottle, clubbing with a candlestick, et cetera.
Most green gremlins are malevolent or amoral, though a few good-natured ones exist. They may be solitary, but are more usually encountered in small groups. Green gremlins sometimes associate with other creatures with similar personalities to their own, such as jackalweres or kenkus, and some powerful chaotic creatures have green gremlin minions or familiars. These mischievous tricksters are hardly reliable allies, so tend to be pets or jesters more than useful servants.
Obsessive Hoarders. All green gremlins love to collect curios. Their hidey-holes contain a bizarre assortment of curious bric-a-brac ranging from mummified remains and pretty stones to finely crafted figurines and a collection of doorknobs. Most items treasured by a green gremlin will be junk with little or no value, but their hoard may include a few objects of actual worth. Valuable items in the lair might include a tool, key or weapon in good condition, a legible book or map, or actual treasure such as coins, jewelry and magic items.