Ancient Hex Dragon

Expounding Hexes. At the start of the dragon's turn, if it used Curse of Spite or Curse of Misery since the end of its last turn, it gains another reaction for 1 minute or until it doesn't use a reaction.

Innate Spellcasting. The dragon's innate spellcasting ability is Charisma (spell save DC 24, +16 to hit with spell attacks). It can innately cast the following Spells, requiring no material components:

at will: Armor of Agathys, Darkness

3/day: Hunger of Hadar, Shadow of Moil

2/day: Enervation, Investiture (can be any, but share the 2/day)

1/day: Finger of Death, Maddening Darkness

Legendary Resistance (3/Day). If the dragon fails a saving throw, it can choose to succeed instead.

Living Arcane Tattoos. The dragon can have two concentration spells up at once, but makes the second concentration check at disadvantage.

Magic Resistance. The dragon has advantage on saving throws against spells and other magical effects.

Vexatious Veins (Recharges on a Short or Long Rest). If the dragon would be reduced to 0 hit points, its current hit point total instead resets to 310 hit points, it recharges its Breath Weapon, it regains any expended uses of Legendary Resistance, and it resets to one reaction per turn (which can be used if it still had reactions remaining before this trait activated). Additionally, the dragon can now use the options in the “Mythic Actions” section as well as it's Vengeful Presence for 1 hour. Award a party an additional 62,000 XP (124,000 XP total) for defeating the dragon after its Vexatious Veins activates.

Multiattack. The dragon can use its Frightful Presence or Vengeful Presence. It then makes three attacks: one with its bite and two with its claws. It can remove attacks to cast a spell (3/day spell for one attack, 2/day for two, or 1/day for 3).

Draining Bite. Melee Weapon Attack: +14 to hit, reach 15 ft., one target. Hit: 12 (1d10 + 7) piercing damage plus 13 (2d8) necrotic damage. The target's hit point maximum is reduced by an amount equal to the necrotic damage taken, and the dragon regains hit points equal to that amount. The reduction lasts until the target finishes 7 long rests. The target dies if this effect reduces its hit point maximum to 0.

Hexing Claw. Melee Weapon Attack: +14 to hit, reach 10 ft., one target. Hit: 10 (1d6 + 7) slashing damage. The target is hexed, and any attacks against it deal an extra 1d4 necrotic damage (including this attack). This can stack up to a maximum of 5d4 damage, and all stacks are removed if the creature heals 20 or more hit points from a single source.

Weakening Tail. Melee Weapon Attack: +14 to hit, reach 20 ft., one target. Hit: 11 (1d8 + 7) bludgeoning damage plus 3 (1d6) necrotic damage. The target's next attack or saving throw within the next minute is reduced by the necrotic damage taken. This does not stack, but the roll is reduced by the highest damage rolled.

Frightful Presence. Each creature of the dragon's choice that is within 120 feet of the dragon and aware of it must succeed on a DC 24 Wisdom saving throw or become frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a creature's saving throw is successful or the effect ends for it, the creature is immune to the dragon's Frightful Presence for the next 24 hours.

Cursed Breath (Recharge 5–6). The dragon exhales poisonous gas in a 90-foot cone. Each creature in that area must make a DC 24 Constitution saving throw, taking 56 (16d6) (16d6) necrotic or radiant damage (dragon's choice) and gaining a status condition on a failed save, or half as much damage and suffers no conditions on a successful one. If the dragon chooses necrotic, the creature is petrified until the end of the dragon's next turn. If it chooses radiant, the creature is stunned until the start of the dragon's next turn.

Mythic: Vengeful Presence. Each creature of the dragon's choice that is within 120 feet of the dragon and aware of it must succeed on a DC 24 Wisdom saving throw or gain a status condition for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a creature's saving throw is successful two times or the effect ends, the creature is immune to the dragon's Vengeful Presence for the next 24 hours.

Roll   Condition

1       Stunned

2       Incapacitated

3       Restrained

4       Blinded

Curse of Spite. The dragon targets a creature that damages it, reducing the target's maximum hit points by 1d6. The reduction lasts until the target finishes 7 long rests. This effect cannot reduce the target's maximum hit points to less than 1.

Curse of Misery. The dragon targets a creature that dealt no damage to it at the end of the target's turn. That creature's speed is reduced by 5 feet. The reduction lasts until the target finishes 7 long rests. This effect cannot reduce the target's speed to less than 1 foot.

The dragon can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The dragon regains spent legendary actions at the start of its turn.

Detect. The dragon makes a Wisdom (Perception) check.

Tail Attack. The dragon makes a tail attack.

Poisonous Wings (Costs 2 Actions). The dragon beats its wings, spreading curses around. Each creature within 15 feet of the dragon must succeed on a DC 24 Dexterity saving throw or take 14 (2d6 + 9) necrotic damage and be poisoned until the end of its next turn. The dragon can then fly up to half its flying speed.

If the dragon's Vexatious Veins trait has activated in the last hour, it can use the options below as legendary actions.

Mythic: Compounding Curses. The dragon can use Curse of Spite or Curse of Misery reaction without using a reaction. It must target the creature that just took a turn, and must use the ability that works against it.

Mythic: Hexing Death (Costs 2 Actions). All creatures within 120 ft. of the dragon must make a DC 24 Wisdom saving throw, taking 8d6 (8d6) necrotic damage on a failed save, or half as much damage on a successful save. Each creature's maximum hit points is reduced by the amount of damage taken. The reduction lasts until the target finishes 7 long rests.

Mythic: Pinnacle of Hate (1/day, Costs 2 Actions). The dragon flies up to its speed and casts Psychic Scream. The dragon must be at least 30 feet in the air to cast this spell.