Chronos

Anchored in Time. The chronos is immune to any spell effect that alters its form or ages it. Further, it can't be affected by the haste, slow, and time stop spell.

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

Winding the Clock. At the start of each of its turns .in combat, the chronos gains 1 Time Charge. It can spend these charges to use certain actions. It loses all charges at the end of combat.

Multiattack. The chronos makes two Claw attacks and uses its Passage of Time once. If Stasis is available, it can use it afterwards.

Claw. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 12 (2d8 + 3) slashing damage.

Passage of Time. The chronos presents its hourglass to one creature that it can see within 60 feet of it. The target must succeed on a DC 16 Wisdom saving throw. On a failure, it takes 45 (7d12) psychic damage, and the creature ages 1d12 years. On a success, it takes half as much damage and doesn't age.

Stasis (Recharge 5-6. The chronos traps a creature in time it can see within 60 feet of it. The target must succeed on a DC 16 Charisma saving throw or become petrified. A petrified target repeats the saving throw at the end of its next turn, ending the effect on itself on a success. On a failure, the effect lasts until the end of its subsequent turn and ends then.

Rewind Time (1/Day; 3 Charges). The chronos flips its hourglass and rewinds time for itself. It then regains all its hit points, ends all effects and spells on it, and recharges all its abilities, except this one.

Hasten (1 Charge). The chronos casts the haste spell. It doesn't require to maintain concentration on the spell and the target doesn't suffer from lethargy at the end of the spell.

Slowing (1 Charge). The chronos casts the slow spell (save DC 16) on a single target. It doesn't require to maintain concentration on the spell and if the target fails the initial save it has disadvantage on the subsequent saves at the end of its turn.