Even the purest of magic cannot exist without the wickedest of curses.
Malicious trespassers who aim to take advantage of the benevolent witch's magic are fated to become impinbunnies. Opposite to faebunnies, these wretched beasts are a bastardized form of the Hollow's enchanting woodland nymphs. Repellent fiends damned to dredge outside the Hollow's gates dedicate their abominable existences to diminishing travelers' chances of achieving their wishes. The most determined of impins even try and corrupt mortal hearts so the witch will view them worthy of damnation.
The malignant power bathing the Forbidden Forest reverses the effect that the Hollow's magic delivers. Caustic and viscious dark magic devours any traveller callous enough to earn the witch's wrath, and remains of their debased form coagulate into cretins known as impin.
They're lesser lifeforms, and their magical ability lies on a spectrum of decent to nonexistent. Most are only equipped with weak hexes; they can hardly defend themselves against the runts of faebuns, so they choose to defend themselves by combining their forces of atrocity. Impins are degenerates despised by all magickind, and thusly only find secure company among other creatures commonly perceived as vermin: reptiles, amphibians, rodents, and insects. Wild impins might adorn their offensive frames with grime like spiderwebs, animal remains, and bug pastes for accessories.