Owlbear
An owlbear is one of the Menagerie's flat refusals to be categorized: the body and temper of a bear, the head and screaming voice of a great owl, and a disposition that improves under no circumstances. It came through The Rift like the rest of the Menagerie and took, with grim enthusiasm, to the pine slopes and cold canyons of the high backcountry, where there is room to hunt and little to argue with it.
The Folk do not domesticate owlbears. A handful of the boldest enclaves have tried, over the centuries, and the lesson is always the same. What the Folk do instead is know where they are, give them a wide berth, and make very sure no human wanders into one's range, because an owlbear is exactly the kind of thing the world above is not allowed to find.
A bear-sized predator with an owl's face and an owl's shriek, glimpsed on a ridgeline or heard screaming in the dark, is a cryptid sighting waiting to happen. More than one "monster in the hills" story that the Concordat has had to quietly bury started with an owlbear that ranged too far down the mountain.
Encountering one
An owlbear hunts by sight and smell, charges what it notices, and is far too stupid and too aggressive to be reasoned with or intimidated. It fights until the fight is clearly lost and only then, grudgingly, breaks off. It defends a kill or a nest with suicidal stubbornness. The danger to the Folk is rarely the owlbear itself, which is a known quantity. It is the witnesses.
Statblock
Run straight from the SRD Owlbear, reframed as a Menagerie beast.
Large monstrosity unaligned
Armor Class 13
Hit Points 59 (7d10 + 21)
Speed 40 ft.
Skills Perception +3
Senses darkvision 60 ft., passive Perception 13
Languages —
Challenge 3
Keen Sight and Smell. The owlbear has advantage on Wisdom (Perception) checks that rely on sight or smell.
Actions
Multiattack. The owlbear makes two attacks: one with its beak and one with its claws.
Beak. Melee Weapon Attack: +7 to hit, reach 5 ft., one creature. Hit: 10 ( + 5) piercing damage.
Claws. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 14 ( + 5) slashing damage.