Wyvern

Clumsy. While not flying, the wyvern is vulnerable to the grappled, prone, and restrained conditions.

Multiattack. The wyvern makes one Bite attack and one Stinger attack. While flying, it can replace one attack with a Claws attack.

Bite. _Melee Weapon Attack:_ +7 to hit, reach 5 ft., one creature. _Hit:_ 11 (2d6+4) piercing damage.

Claws. _Melee Weapon Attack:_ +7 to hit, reach 5 ft., one target. _Hit:_ 13 (2d8+4) slashing damage.

Stinger. _Melee Weapon Attack:_ +7 to hit, reach 15 ft., one creature. _Hit:_ 15 (2d10+4) piercing damage plus 18 (4d8) poison damage. The target must succeed on a DC 15 CON save or be poisoned for 1 minute. A poisoned creature can repeat the save at the end of each of its turns, ending the effect on itself on a success.

Reflexive Tail Whip. When a creature moves into a space within 15 feet of the wyvern, it can whip its tail at the creature. The target must succeed on a DC 15 STR save or be knocked prone.