Archive Guardian

Construct Nature. The swarm doesn't require air, food, drink, or sleep.

Death Burst. Dexterity Saving Throw: DC 20, each creature within 10 feet. Failure: 27 (8d6) Psychic damage. Success: Half damage and no additional effect.

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

Living Archive. When the Archive Guardian is created, it gains 15 temporary hit points for each Living Tome Swarm consumed during its formation. While it has temporary hit points, it has advantage on Intelligence and Wisdom saving throws.

Living Records. Whenever a creature within 30 feet casts a spell, the Guardian learns that spell until the end of its next turn. The next time it makes a melee attack before then, it deals an extra 1d8 force damage.

Multiattack. The wraith makes two Archive Slam attacks.

Archive Slam. Melee Attack Roll: +8, reach 10 ft. Hit: 18 (3d8 + 5) Bludgeoning damage plus 11 (2d10) Psychic damage. The target must succeed on an Intelligence Saving Throw: DC 18. Failure: become Stunned condition until the start of its next turn as impossible memories and unrealized futures flood its mind. Success: no additional effects.

Rewrite Fate (Recharge 5–6). Wisdom Saving Throw: DC 18, each creature within 60 feet. Failure: 27 (8d6) Psychic damage and the creature can’t take reactions and its speed is halved until the end of its next turn. Success: Half damage and no additional effects.