Flyby. The sharn doesn’t provoke an opportunity attack when it flies out of an enemy’s reach.

Legendary Resistance (2/Day). If the Sharn fails a saving throw, it can choose to succeed instead.

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

Regeneration. The sharn regains 10 hit points at the start of its turn if it has at least 1 hit point.

Three Heads. The sharn has advantage on Wisdom (Perception) checks and on saving throws against being blinded, charmed, deafened, frightened, stunned, and knocked unconscious.

Multiattack. The sharn makes four attacks: three with its bite and one with its claws.

Claw. Melee Attack: +8 to hit, reach 10 ft. , one target. Hit: 7 (2d6 + 5) necrotic damage.

Bite. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 6 (2d8 + 5) piercing damage plus 14 (4d6) necrotic damage, and the target must succeed on a DC 16 Constitution saving throw or become poisoned for 1 minute. A target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Adaptive Blue Bolt. Ranged Spell Attack: +8 to hit, range 120 ft., one target. Hit: 28 (8d6) necrotic damage. If the target is a creature, it must succeed on a DC 16 Constitution saving throw against disease or become poisoned until the disease is cured. Every 24 hours that elapse, the creature must repeat the saving throw, reducing its hit point maximum by 5 (1d10) on a failure. This reduction lasts until the disease is cured. The creature dies if the disease reduces its hit point maximum to 0.

Hex Portal (Bonus Action). Ranged 30'. The sharn creates a hexagonal window of blue light that  it can attack through as if it were in that portal's space. As a bonus action, it can move one portal up to 30'. Portals don't block line of sight, line of effect, or enemy movement. A sharn can maintain up to three such portals at a time and it can close as many as it wishes with a no action cost.

Spell Reflection. If the sharn makes a successful saving throw against a spell, or a spell attack misses it, the sharn can choose another creature (including the spellcaster) it can see within 60 feet of it. The spell targets the chosen creature instead of the sharn. If the spell forced a saving throw, the chosen creature makes its own save. If the spell was an attack, the attack roll is rerolled against the chosen creature.

The sharn 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 sharn regains spent legendary actions at the start of its turn.

Teleport (Costs 2 Actions). The sharn magically teleports, along with any equipment it is wearing or carrying, up to 120 feet to an unoccupied space it can see.

Move. The sharn moves up to its half speed without provoking opportunity attacks.

Frightening Gaze (Costs 2 Actions) The sharn fixes his gaze on one creature he can see within 30 feet of him. The target must succeed on a DC 16 Wisdom saving throw against this magic or become frightened for 1 minute. The frightened target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a target's saving throw is successful or the effect ends for it, the target is immune to sharn's gaze for the next 24 hours.