Chronotyryn

Dual Action. At the start of combat, the chronotyryn rolls for initiative twice, occupying two places in the initiative order and taking two turns per round. Additionally, the chronotyryn can concentrate on two spells at once.

Innate Spellcasting. The chronotyryn's innate spellcasting ability is Charisma (spell save DC 19). The chronotyryn can cast the following spells, requiring no material components:

At will: blink, detect magic, teleport
3/day each: blur, feeblemind, time stop
1/day: imprisonment (chaining)

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

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

Magic Weapons. The chronotyryn's weapon attacks are magical.

Spellcasting. The chronotyryn is a 12th-level spellcaster. Its spellcasting ability is Charisma (spell save DC 19, +11 to hit with spell attacks). The chronotyryn knows the following sorcerer spells:

Cantrips (at will): dancing lights, mage hand, mending, ray of frost, resistance
1st level (4 slots): fog cloud, grease, magic missile, shield
2nd level (3 slots): acid arrow, enhance ability, web
3rd level (3 slots): counterspell, lightning bolt, slow
4th level (2 slots): black tentacles, greater invisibility, ice storm
5th level (2 slots): cloudkill, hold monster
6th level (1 slot): disintegrate

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

Wakeful. When one of the chronotyryn's heads is asleep, its other head is awake.

Multiattack. The chronotyryn makes three attacks: one with its bite and two with its talons or flechettes.

Bite. Melee Weapon Attack: +11 to hit, reach 5 ft., one target. Hit: 10 (1d8 + 6) piercing damage.

Talons. Melee Weapon Attack: +11 to hit, reach 5 ft., one target. Hit: 9 (1d6 + 6) slashing damage.

Flechettes. Ranged Weapon Attack: +9 to hit, range 60 ft., one target. Hit: 11 (2d6 + 4) slashing damage.

Sonic Screech (Recharge 5-6). The chronotyryn unleashes an ear-splitting screech. Each creature within 20 feet of the chronotyryn must make a DC 18 Constitution saving throw. On a failed save, a creature takes 35 (10d6) thunder damage and is deafened for 1 minute. On a successful save, a creature takes half as much damage and is not deafened.

Reactive. The chronotyryn can take a reaction on every creature's turn in combat.