Uthrifal

Amphibious. The dragon can breathe air and water.

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

Living Shadow. While in dim light or darkness, the dragon has resistance to damage that isn’t force, psychic, or radiant.

Shadow Stealth. While in dim light or darkness, the dragon can take the Hide action as a bonus action.

Sunlight Sensitivity. While in sunlight, the dragon has disadvantage on attack rolls, as well as on Wisdom (Perception) checks that rely on sight.

Innate Spellcasting. Uthriful can innately cast the following spells, requiring no somatic or material components.

At will: Darkness, Shield, Dispel Magic

1/day: Haste, Plane Shift, Blight (7th level)

Multiattack. The dragon can use its Frightful Presence. It then makes three attacks: one with its bite and two with its claws.

Bite. Melee Weapon Attack: +17 to hit, reach 15 ft., one target. Hit: 20 (2d10 + 9) piercing damage plus 9 (2d8) necrotic damage.

Claw. Melee Weapon Attack: +17 to hit, reach 10 ft., one target. Hit: 16 (2d6 + 9) slashing damage.

Tail. Melee Weapon Attack: +17 to hit, reach 20 ft., one target. Hit: 18 (2d8 + 9) bludgeoning damage.

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.

Shadow Breath (Recharge 5–6). The dragon exhales acid in a 90-foot cone. Each creature in that line must make a DC 24 Dexterity saving throw, taking 117 (26d8) necrotic damage on a failed save, or half as much damage on a successful one. A humanoid reduced to 0 hit points by this damage dies, and an undead shadow rises from its corpse and acts immediately after the dragon in the initiative count. The shadow is under the dragon’s control.

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.

Wing Attack (Costs 2 Actions). The dragon beats its wings. Each creature within 15 feet of the dragon must succeed on a DC 24 Dexterity saving throw or take 16 (2d6 + 9) bludgeoning damage and be knocked prone. The dragon can then fly up to half its flying speed.