Swarm the Unafflicted. Vileblood Wretches can make an attack with advantage against a foe, if that creature is currently grappled by another Vileblood creature.

Bloodlust. Upon successfully biting a creature, the Vileblood gains 2d10-2 hitpoints and enters its Blooded form. In this form, the Vileblood Wretch has advantage on Strength saving throws as well as Dexterity, gains +3 to its Strength, Dexterity, and Constitution scores, and can utilize its Blooded Moveset. While in this frenzied state, however, the Vileblood Wretch is vulnerable to Slashing damage of all types, and has disadvantage on Wisdom and Intelligence saving throws.

The Vileblood Curse. Sorry souls bitten successfully must make a DC 16 Constitution saving throw and take 2d10 necrotic damage, taking half damage on a successful save. On a failed save, full damage is taken, and a d100 is rolled. If the value rolled is 26-100, nothing happens. If the roll is 1-25, the foe is now affected by the Vileblood Curse.

Swipe. Melee Weapon Attack:  +2 to hit, range 5 ft., one target. Hit 5 (1d6+2) bludgeoning damage. Target must make a DC 14 Strength Saving Throw. If failed, the target is now grappled.

Bite. Melee Weapon Attack: +2 to hit, range 5 ft., one target. Hit 8(2d6+2) piercing damage. Can only be used on a grappled target.

Blooded Moveset:

Multiattack. The Vileblood  Wretch can use its Regurgitation attack or make two Slash attacks.

Regurgitation. The Vileblood Wretch spits up a mixture of blood and acid in a 15 ft. cone. All creatures within the cone must make a DC 14 Dexterity saving throw, taking 12(3d8) acid damage on a failed save, and half on a successful one. Failure of the save also results in the affected creature becoming blinded until the end of their next turn. The Vileblood Wretch reverts to its "withered," state after using this action.

Slash. Melee Weapon Attack +4 to hit, range 5 ft., one target. Hit 10(2d6+4) slashing damage.