Flyby. The Abyssal Giant Vulture doesn't provoke opportunity attacks when it flies out of an enemy's reach.
Keen Sight and Smell. The Abyssal Giant Vulture has advantage on Wisdom (Perception) checks that rely on sight or smell.
Pack Tactics. The Abyssal Giant Vulture has advantage on an attack roll against a creature if at least one of the Abyssal Giant Vulture's allies is within 5 feet of the creature and the ally isn't incapacitated.
Stench. Any creature other than an Abyssal Giant Vulture that starts its turn with in 5 feet of the vulture must succeed on a DC 12 Constitution saving throw or be poisoned until the start of the creature's next turn. On a successful saving throw, the creature is immune to the stench of all Abyssal Giant Vulture for 1 hour.
Multiattack. The Abyssal Giant Vulture makes two attacks: one with its beak and one with its talons.
Beak. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 10 (2d6 + 3) piercing damage.
Talons. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 14 (2d10 + 3) slashing damage.
Stunning Screech (1/Day). The Abyssal Giant Vulture emits a horrific screech. Each creature within 20 feet of it that can hear it and that isn't a Fiend must succeed on a DC 13 Constitution saving throw or be stunned until the end of the Abyssal Giant Vulture's next turn.
Oil Slick. As a reaction, if an enemy of Abyssal Giant Vulture walks within 10ft of the creature, it can begins to puff out all its feather and violently shakes its body ending with its wings flinging outwards as it begins to take flight allowing the vulture to move up to 10ft of its flying speed.
The violent shaking causes the black, oily and smelly substance to fling off its feathers and body to cover the ground in a 10ft circle centered on itself and turns it into difficult terrain. When the black, oily and smelly substance appears, each creature standing in its area must succeed on a Dexterity saving throw or fall prone. A creature that enters the area or ends its turn there must also succeed on a Dexterity saving throw or fall prone.
This affected area also has the effect of the special trait Stench.
Description
These Abyssal Giant Vulture have fed on abyssal touched creatures and/or live next to an open portal to the Nine Hells and/or The Abyss where the continual energy that corrupts the nearby land has also infect these creatures. Either way their normal appearance has been corrupted and defiled. These creatures also have been heard at times to speak one or two words at a time in Abyssal; it is assumed that they have learned to mimic what is in their area.
An Abyssal Giant Vulture's monstrous form seems to be mutating into a Vrock. It's normal tough tendons and bones bird foot are split apart at the top to allow for more leg muscle to grow and more articulation of the feet. This sometimes makes for an Abyssal Giant Vulture to have to different size legs which cause them to hobble if walk but note it does not slow the creature down.
The feathers on the Abyssal Giant Vulture's head, chest, sides are patchy and missing leaving a tougher leather hide growing in its place. The creature's tail is also losing its feathers revealing the flight feather shafts as the ones on the edges appear to be rotting off as the ones in the middle are growing in girth and leathery hide. These new leather feather shafts still have flight feathers at the tip to still help with their flying. Their normal wing flight feathers become thicker and slicker with a black, oily and smelly substance that protects the wings for the elements; the Abyssal Giant Vulture also takes time to groom this oily substance as well as fluid from its rotting meals around its body that is missing feathers.
The beak of the Abyssal Giant Vulture is elongated and has developed spikes around the edges. With the missing feathers on the face it shows budding spikes along the face where it is starting to grow harden spikes instead of feathers for protection, this continues through the Abyssal Giant Vulture's body. Though these creatures do not have arms like Vrocks their leathery chest shows that the sternum has mutated and outgrown the body stretching the skin around it and some points grown out like budding spikes.
An Abyssal Giant Vulture has advanced intelligence and a malevolent bent. Unlike its smaller kin, it will attack a wounded creature to hasten its end. Abyssal Giant Vulture have been known to haunt a thirsty, starving creature for days to enjoy its suffering. Just like the other vultures they stay in packs to hunt and scavenge around their domain often bringing food back to their nest.