Corrupted Faerie Dragon

Legendary Resistance (3/Day, or 4/Day in Lair). 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.

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

Multiattack. The dragon makes two Rend attacks, followed by a Psionic Strike.

Rend. Melee Weapon Attack: +12 to hit, reach 5 ft., one target. Hit: 12 (2d4 + 7) [necrotic] damage plus 5 (2d4) [psychic] damage, and the target's Strength score decreases by 1d4. The target dies if this reduces that score to 0. If a Humanoid is slain by this attack, a Shadow rises from the corpse 1d4 hours later.

Psionic Strike. Intelligence Saving Throw: DC 18, one creature within 60 feet of the dragon. Failure: 12 (5d4) psychic damage, and the target is Charmed by or Frightened of the dragon (dragon's choice) until the end of the dragon's next turn. If the dragon damages a creature Charmed in this way, the effect ends early.

Misery Breath (Recharge 5–6). Wisdom Saving Throw: DC 18, each creature in a 60-foot Cone. Failure: 45 (18d4) psychic damage and the target has the Incapacitated condition. The target repeats the save at the end of each of its turns, ending the effect on itself on a success. After 1 minute, it succeeds automatically. While Incapacitated in this way, the target uses all its movement on each of its turns to move in a random direction.

Spellcasting. The dragon casts one of the following spells, requiring no Material components and using Charisma as the spellcasting ability (spell save DC 18, spell attack modifier +10):

• At will: Dancing Lights, Mage Hand, Minor Illusion, Charm Person, Command, Sleep
• 3/day each: Enthrall, Hold Person, Nystul's Magic Aura, Suggestion, Bestow Curse,  Hypnotic Pattern, Vampiric Touch
• 1/day each: Blight, Confusion, Dominate Beast, Greater Invisibility, Hallucinatory Terrain, Dream, Mislead, Modify Memory

Misty Step (3/Day). The dragon casts Misty Step, using the same spellcasting ability as Spellcasting.

Superior Invisibility. The dragon casts Invisibility on itself, requiring no spell components and using the same spellcasting ability as Spellcasting.

Counter-Magic. The dragon casts Shield in response to the spell's trigger, using the same spellcasting ability as its Spellcasting. When it does so, the dragon can cast Charm Person or Command instead.

Legendary Action Uses: 3 (4 in Lair). Immediately after another creature's turn, The corrupted faerie dragon can expend a use to take one of the following actions. The shadow dragon regains all expended uses at the start of each of its turns.

Drain Mind. The dragon makes one Psionic Strike attack. If the target fails its saving throw, the dragon regains its Reaction (if expended) and has advantage on the next saving throw it makes.

Illusory Dance. The dragon moves up to its speed, then makes one Rend attack with Advantage.

Minor Spellcasting. The dragon uses its Spellcasting to cast a single spell it can cast At Will. Afterwards, it cannot use this ability again until the start of its next turn.

Major Spellcasting (Costs 3 Actions). The dragon uses its Spellcasting.