Timeless Chronomancer

Magic Resistance. The chronomancer has advantage on saving throws against spells and other magical effects.
Spellcasting. The chronomancer is a 20th-level spellcaster. Its spellcasting ability is Intelligence (save DC 18, +10 to hit with spell attacks). The chronomancer has the following wizard spells prepared:
Cantrips (at will): blade ward, light, mage hand, ray of frost, prestidigitation
1st level (4 slots): detect magic, expeditious retreat, magic missile, shield
2nd level (3 slots): hold person, misty step
3rd level (3 slots): blink, haste, slow
4th level (3 slots): banishment, dimension door
5th level (3 slot): cone of cold, wall of force
6th level (1 slot): globe of invulnerability
7th level (1 slot): teleport
8th level (1 slot): maze
9th level (1 slot): time stop
Stretch Time (Recharge 5-6). The chronomancer can take on additional action on its turn.

Expose Paradox (Recharge 5-6). The chronomancer choses one creature it can see within 60 feet of it, revealing to it a paradox in the space-time continuum. The target must make a DC 18 Wisdom saving throw, taking 42 (12d6) psychic damage on a failed save, or half as much damage on a successful one.

Rewind. When the chronomancer or another creature makes an attack roll, saving throw, or ability check, it must remake the roll and use the new result.