Akaasit

Immutable Form. The akaasit is immune to any spell or effect that would alter its form.

Unfixed in Time. To those properly fixed in time, the akaasit flickers in and out of time, its position never fully clear. Attack rolls against the akaasit have disadvantage. If it is hit by an attack, this trait ceases to function until the start of its next turn.

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

Multiattack. The akaasit makes two arm blade attacks.

Arm Blade. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 13 (2d8 + 4) slashing damage plus 3 (1d6) force damage.

Time-Assisted Counterattack. The akaasit's awareness of the near future allows it to see attacks before they happen. When a creature the akaasit can see attacks it while within 5 feet of it, the akaasit can attack the creature before the creature's attack hits. The akaasit makes a single arm blade attack against the creature. If the creature is reduced to 0 hp as a result of the akaasit's attack, the creature's attack doesn't hit the akaasit.