Skeletal Appearance. While the skeletal owlbear is lying still, it is indistinguishable from a mundane skeletal corpse. It can still be detected by a detect evil and good spell, or similar magic.

Undead Fortitude. If damage reduces the skeletal owlbear to 0 hit points, it must make a Constitution saving throw with a DC of 5 + the damage taken, unless the damage is radiant or from a critical hit. On a success, it drops to 1 hit point instead.

Undead. The skeletal owlbear does not require air, sleep, food or drink. 

Multiattack. The skeletal owlbear makes two Ravage attacks, or one Frightful Presence attempt.

Ravage. Melee Attack Roll: +9, reach 5 ft. Hit: 15 (2d8 + 6) Slashing damage. If the target is a Huge or smaller creature and the skeletal owlbear moved 20+ feet straight toward it immediately before the hit, the target takes an extra 9 (2d8) Slashing damage and has the Prone condition.

Frightful Presence. Each creature of the skeletal owlbear's choice that is within 120 feet of the it and aware of it must succeed on a DC 16 Wisdom saving throw or become frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a creature's saving throw is successful or the effect ends for it, the creature is immune to the skeletal owlbear's Frightful Presence for the next 24 hours.