The wyvern, a none-too-bright, beast-grade member of the dragon family, is in most respects a basic brute. But there’s a subtlety in its constellation of features that’s easy to overlook.
Wyverns have a basic “walking” speed of 20 feet per turn but a flying speed of 80 feet. With that kind of gap, there’s no reason for it to hold still and engage in stationary melee, as other high-Strength, high-Constitution brutes are happy to do. Wyverns are melee fighters, but they’re strafing melee fighters that never touch the ground if they can help it, nor do they remain within reach (and therefore engagement range) of their enemies.
In addition to their teeth and claws, wyverns have scorpioid venomous stingers in their tails, which can do massive poison damage on top of their typical-for-a-Large-creature piercing damage. That’s a no-brainer: A wyvern will always try to get at least one stinger attack in. But the wyvern’s Multiattack action offers the option of substituting a claw attack for either element of the basic bite/sting combo.
At first glance, it seems like a good deal: the wyvern’s claws do slightly more damage than its bite (d8’s rather than d6’s). But look at the reach on those attacks. The claws have a 5-foot reach, so the wyvern has to get right up to its enemy to use them. The bite, on the other hand, has a 10-foot reach, as does the stinger. What this means is that a wyvern can do a flyby bite/stinger attack (despite not having the Flyby feature) without ever coming closer than 10 feet to its opponent, which means without coming within his or her reach, which means not leaving his or her reach, which means not incurring an opportunity attack. Thus, even though the wyvern doesn’t have Flyby, it can accomplish exactly the same effect, thanks to the 10-foot reach on its attacks. (Except in the unlucky instance in which its chosen prey is wielding a polearm. Unfortunately, wyverns aren’t clever enough to alter their tactics to fit new, unexpected facts. This modus operandi is the only one they’ve got.)
Does this mean the wyvern never has any reason to attack with its claws? Not at all. If it’s grounded somehow (knocked prone, grappled or restrained) and its foes have closed with it, once it gets its movement back it will make a claw/stinger Multiattack instead of its usual bite/stinger Multiattack, for that extra couple of points of expected damage, in the process of launching itself into the air again—heedless of opportunity attacks, because at worst, it can only take one hit per opponent while it’s taking off. If it stays on the ground, it risks taking a lot more than that if its opponents have Extra Attack, and if they’re fighting a monster with a challenge rating of 6, they probably do. If it can’t get airborne, it can only bite/sting.
Like other predators, the wyvern is primarily interested in a meal, which means going after the weakest-looking individual in a group—ideally, one who’s isolated or oblivious. Once it’s chosen its prey, it’s going to single that individual out for the full measure of its aggression. When the prey is rendered unconscious, the wyvern will forgo its Multiattack in favor of a grapple attack (with advantage). If the grapple succeeds, the wyvern flies off with its prey back to wherever it nests. If the prey is a Small creature—say, a halfling or gnome—the wyvern can fly away at full speed. Otherwise, its speed is halved, but it can still go 80 feet in a turn by Dashing through the air.
Wyverns are fierce and bad-tempered, but they still want to live. Seriously wound one (reduce it to 44 hp or fewer), and it will Dash off in search of easier prey.
Next: centaurs, another Monster Manual omission.