What a difference a letter makes! Dangerously close alphabetically to the first Pathfinder Bestiary’s froglike boggard, Occult Bestiary’s boggart hews closer to the original folkloric bogey. Possibly born of corrupted brownies (a reeeally nice throwback to the incomparable Roger E. Moore’s original write-up in Dragon #54), boggarts haunt farmsteads and nearby wetlands, where they feed on the negative psychic energy created by the disruption and trauma thy cause. (Interestingly, the boggart retains a brownie’s focus on a particular family—Occult Bestiary describes how unmoored boggarts are much more likely to kidnap and even eat victims, whereas a boggart with a family to obsess over is content to merely make them miserable.)
A boggart’s abilities are centered around the illusions it creates and its ability to position others—dragging with its long arms and Improved Drag, paralyzing with hold person, and bull-rushing, grappling, or otherwise repositioning foes with telekinetic maneuver and Combat Expertise. So when fighting a boggart—assuming you can even find it in the first place—you’re dealing with a fey that truly has the upper hand in its own domain.
PCs don't usually engage with their families much—being an orphan is a great origin story, and if a player does give his PC’s family some backstory you can almost bet they’ll be dead or betray him by level 10—and engaging with an NPC’s family is just asking for a) more death, b) ghost hauntings, or c) the dreaded annoying-kid escort mission. The boggart is a great excuse for a family-focused adventure that keeps the stakes relatively low.
A boggart has abducted children and murdered their parents. But when adventures are sent to dispatch him, a coalition of grigs, pixies, sprites, and other goodly fey works to undermine their efforts—even going so far as to take up nonlethal arms in his defense. The fey don't want the boggart slain; they want to find him a home and a family to give him purpose. (They will even volunteer to keep the misery he causes to manageable levels…but (being faeries) they only offer this if pressed.)
After luring a berserker into a quagmire, a boggart steals the warrior’s horned helm…and instantly becomes a brownie, having been zapped by the helm of opposite alignment that made the berserker so bloodthirsty in the first place. He is delighted with the turn of events and even finds a family farm to discreetly serve. His boggart sisters, meanwhile, are horrified. They do everything they can to both make his chosen family miserable and reverse their brother’s curse (which, as the helm is a very low-powered specimen, they have a decent chance of doing with the negative emotions they are generating fueling their efforts).
Cascade Manor is a haunting complex of building perched above churning rapids. When the old lord died he bequeathed his title and lands to a nephew, but gave much of the wealth to a school for foundlings and disinherited children. The grasping nephew and his sister hate their obligation to the students and have purposefully staffed the school with martinets, scolds, and tyrants. The resulting stew of ill feeling and sorrow has in turn drawn the attention of a boggart and a bloody bones (treat as a variant ghoul that lurks under stairways and hunts children who catch sight of it). The boggart mentally tortures a particular child for days before handing it over to the bloody bones for its repast, then the cycle begins anew. Meanwhile, the new lord and lady of Cascade Manor have so far shown no concern over the schoolmaster’s reports of missing children.
—Occult Bestiary 11
For you history buffs out there, a quick glance through Dragon #54 also reveals AD&D stats for the jabberwock and what appears to be some of the first public write-ups of the Forgotten Realms’ deities courtesy of Ed Greenwood—all the way back in October of 1981, no less!
For another take on the bloody bones, Tim Hitchcock’s Pathfinder Module Hungry Are the Dead borrows the Tome of Horrors’s version, and apparently frequent commenter demiurge1138 statted one up for 3.5 over at EN World.