I home-brewed a Middle-earth alternative to the standard D&D 5E wyvern:
Wyvern
Large dragon
STR 19 (+4)
DEX 12 (+1)
CON 18 (+4)
INT 5 (-3)
WIS 12 (+1)
CHA 6 (-2)
ARMOUR CLASS 13
HIT POINTS 105 (10d12 + 40)
SPEED 20 ft., fly 80 ft.
SKILLS Perception +4
CONDITION IMMUNITIES poisoned
SENSES darkvision 60 ft., passive Perception 14
LANGUAGES --
CHALLENGE 4 (1,100 XP, proficiency bonus +2)
POISON. The Wyvern's bite inflicts 7 (3d4) poison damage, and the target must succeed on a Constitution saving throw (DC 14) or be poisoned for 1 hour. If the saving throw fails by 5 or more, the target cannot regain hit points and has disadvantage on death saving throws while poisoned in this way.
ACTIONS
MULTIATTACK. When flying, the Wyvern can make two attacks, one with its bite and one with its claws. On the ground, the Wyvern only attacks with its bite.
BITE. Melee Weapon Attack: +6 to hit. reach 5 ft., one target. Hit: 2d6 + 4 piercing damage. If the target is Large or smaller, it must make a Strength saving throw (DC 14) or be knocked prone.
CLAWS. Melee Weapon Attack: +6 to hit, reach 10 ft., one target. Hit: 2d8 + 4 slashing damage. If the target is Large or smaller, it is grappled (escape DC 14) and the Wyvern cannot use this attack on another target.
Whether they were bred by Morgoth or are some unnatural offshoot of dragonkind, Wyverns are smaller, four-limbed (two wings and two legs) cousins to the great Dragons of the North. Wyverns can be distinguished by their lack of forelegs and by their venomous bite. Unlike their greater kin, Wyverns only possess animal intelligence.