Rampage.

When the demon reduces a creature to 0 hit points with a melee attack on its turn, the gnoll can take a bonus action to move up to half its speed and make a bite attack.

Chaotic carnage

On each of its turns, the demon uses all its movement to move toward the nearest creature. Roll a d10 at the start of each of the demon's turns to determine its action for that turn: At the start of its turn, the demon can choose to make a Wisdom saving throw, with a dc of 13. On a success, they can act as they wish.

1-3. The demon makes three attacks with its claws against one random target within its reach. If no other creatures are within its reach, the demon flies into a rage and gains advantage on all attack rolls until the end of its next turn.

4-5. The demon makes one attack with its claws against every creature within its reach. If no other creatures are within its reach, the giant makes one claw attack against itself.

6-7. The demon makes one attack with its bite against one random target within its reach. If no other creatures are within its reach, its eyes glaze over and it becomes stunned until the start of its next turn.

8-10. The demon makes three attacks against one random target within its reach: one attack with its bite and two with its bites. If no other creatures are within its reach, the demon flies into a rage and gains advantage on all attack rolls until the end of its next turn.

Bite. Melee Weapon Attack: +2 to hit, reach 5 ft., one target. Hit: 3 (1d6) piercing damage.

Claws. Melee Weapon Attack: +2 to hit, reach 5 ft., one target. Hit: 5 (2d4) slashing damage.

blood wave (1/Day). A 10­-foot radius of spilling blood extends out from the demon. The wave spreads around corners, and its area is difficult terrain. It lasts for 1 minute. Any creature that starts its turn in that area must succeed on a DC 11 Wisdom saving throw or be frightened until the start of its next turn.