Here’s a rather different take on bugbears.
Svelte, silver-furred killers, bugbears glide out of the woods on four legs, then rise on their haunches to slash at their enemies with long, razor-sharp claws normally retracted into their forepaws. Instead of the brutish brawn of an orc or the feral unpredictability of a tree-goblin, bugbears move with grace and purpose, wielding their foot-long claws with the skill of a fencer.
Bugbears attack small or otherwise weak groups, and as strange as it may seem, the urban myth is true: they only ever take a single victim away with them. Others may be killed or simply knocked unconscious by the bugbears’ massive bulk. The bugbears’ victim is never seen again.
I know of two plausible explanations for this behavior. One theory states that the bugbears simply eat the victim, and that a single humanoid is a sufficient meal for a family of bugbears.
The other theory, championed most strongly by the scholar Darro Cater, points out two strange but true facts: not even a shred of any victim has ever been found, and bugbears act with definite intelligence. There are no records of bugbears speaking—other than old wives’ tales to scare children—but they do attack and defend themselves very well, even retreating as a group when the odds turn against them.
Darro believes that bugbears sacrifice their victims in a magical ritual that consumes the victims’ bodies. Stranger things are true.
Bugbears have only ever been seen in groups of 3 to 4. These are likely family units, and are more than enough of a threat for all but the most seasoned adventurers.