Culex, Lord of the Flies

Resting Place. When Culex drops to 0 hit points and isn’t in his resting place, he bursts into a cloud of death and teleports to his resting place. While in his resting place, Culex is stable. After spending 1 hour in his resting place with 0 hit points, he regains 1 hit point.

Blood Sacrifice (3/Day). Culex is surrounded by three floating pools of shimmering blood which can take the form of spears at his command. When Culex fails an ability check or saving throw, he can choose to destroy one of these pools of blood and succeed on the ability check or saving throw instead. Once Culex destroys all three spears, he can’t use his Sanguinus attack or Blood Sacrifice until the next dusk, when he manifests any destroyed spears.

Pestilence Incarnate. The god's true form is that of a huge, round and bloated, mosquito-like creature, though he can take the form of a medium humanoid stricken with visible disease, such as leprosy or vampirism.

Multiattack. Culex makes two Unliving Proboscis attacks, and he can make one Sanguinus attack for each Blood Sacrifice use he has remaining.

Unliving Proboscis. Melee Weapon Attack: +12 to hit, reach 5 ft., one target. Hit: 13 (2d6 + 6) piercing damage plus 14 (4d6) necrotic damage. If the target is a creature, their hit point maximum is reduced by a number equal to the necrotic damage taken, and Culex regains hit points equal to that number. This reduction lasts until reversed by a greater restoration spell, or a similar effect. The target dies if this effect reduces their hit point maximum to 0. A humanoid slain in this way rises the following midnight as a vampire spawn under Culex's control.

Sanguinus. Ranged Spell Attack: +12 to hit, range 60 ft., one target. Hit: 10 (3d6) piercing damage, and if the target is a creature, they are knocked prone and restrained as a spear of blood impales them. A creature can attempt to free themself or another creature within their reach by using an action or a bonus action to make a DC 20 Strength Athletics check. On a success, the creature is freed and the restrained condition ends for them. The creature is also freed if Culex summons that spear to attack another target or destroys it using Blood Sacrifice.

Call To the Grave. Culex targets one creature he can see within 30 feet of him and who can see him. The target must make a DC 20 Wisdom saving throw. On a failed save, the creature uses their reaction, if available, to make a melee attack against themselves.

Flight of the Pest. Culex flies up to his speed without provoking opportunity attacks.

Withering Stare. When Culex is hit by an attack by a creature he can see within 60 feet of him, his eyes bore into the creature. The target must succeed on a DC 20 Wisdom saving throw or take 10 (3d6) necrotic damage.

Villain Actions

Culex has three villain actions. He can take each action once during an encounter after an enemy’s turn. He can take these actions in any order but can use only one per round.

Action 1: Bloodstained. Culex causes blood to explode in a 20-foot-radius sphere centered on a point he can see within 120 feet of him. Creatures who aren’t Undead in that area must succeed on a DC 20 Dexterity saving throw or be bloodstained until the end of his next turn. Culex has advantage on attack rolls against bloodstained creatures, and bloodstained creatures have disadvantage on saving throws against Culex's Call To The Grave bonus action.

Action 2: Swarm of The Damned. Culex transforms into a huge swarm of thousands of mosquitos and biting bugs. When he does, he releases any creature he was grappling, and if Culex was grappled or restrained, that effect ends for him. He then flies up to twice his speed to an unoccupied space. During this move, Culex ignores difficult terrain doesn’t provoke opportunity attacks, and can move through creatures and objects. Each creature Culex passes through must make a DC 20 Dexterity saving throw, taking 36 (8d8) necrotic damage on a failed save, or half as much damage on a successful one. At the end of this movement, he transforms back into his previous form.

Action 3: The End is Nigh. Culex fills the area within 60 feet of him with thick swirling mists. Creatures, besides undead, within the mist cannot receive supernatural healing and reduce their maximum hit points by 10 (3d6) whenever they end their turn inside the mist.