There is an official buggane in Pathfinder, but it bears less resemblance to the Manx folklore. I’ve used both versions, calling the Paizo one a “moldywarp”, after an old-fashioned name for moles.]
Buggane This hulking, shaggy creature
resembles a great humanoid mole with a tusked snout and broad claws on its
muscular forearms. Its beady eyes glow with orange light, and a great mane of
black hair runs down its back.
Even
unholy lands require guardians. The bugganes are the wardens of such unlovely
and unloved locations as unconsecrated graveyards, the sites of human sacrifice
and abandoned temples of evil deities. Nasty and peevish creatures, bugganes
repel all intruders through a combination of trickery and physical violence.
Natural shapeshifters, they use this talent in conjunction with their illusory
abilities to pose as lost livestock or helpless travelers, the better to lure a
victim into a vulnerable position. In combat, bugganes use their Spring Attack
feat to its fullest, diving beneath the earth between strikes. Bugganes are
such sore losers that they would rather die than be defeated, even in a contest
of wits or skill instead of strength, and they are capable of killing
themselves in an explosive display of spite by tearing off their head and
throwing it like a missile.
Almost
all bugganes are pure evil, and unholy energy saturates their very bodies.
Although they cannot create undead, bugganes are often found alongside them;
the undead attracted to or created by the unhallowed lands bugganes favor are
conscripted by the wicked fey into joining the vigil. It is rumored that many
bugganes were once more peaceful fey, such as dryads, nymphs or sprites,
corrupted into their current monstrous forms by whatever magic ruined their
land. Conversely, it may be possible to restore a buggane to its original body
by ending the curse on their territory. If this is the case, however, no
buggane has ever confirmed it. Tall and broad, bugganes stand over nine feet
tall and weigh about half a ton.
Buggane Boons and Banes A buggane
will occasionally befriend another evil creature that dwells in its desecrated
land, and these allies receive its boon if they especially curry the selfish
creature’s favor. Most bugganes simply kill and eat their defeated enemies
rather than curse them, but they are crafty enough to try and trick those that
attempt to negotiate them into accepting their bane.
Boon: You gain the desecrated strength
quality of a buggane. This boon lasts for 1 day.
Bane: You no longer heal hit point
damage naturally through rest, and positive energy heals half the normal amount
when used on you. This bane is permanent until dispelled.
The Creature Codex 