Clockwork Guardian

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

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

Clockwork Repair. At the start of each of its turns, the Clockwork Guardian regains 5 hit points if it has at least 1 hit point.

Multiattack. The guardian makes two slam attacks.

Slam. Melee Weapon Attack: +10 to hit, reach 5 ft., one target. Hit: 19 (3d8 + 6) bludgeoning damage.

Gear Grind (Recharge 5-6). The guardian spins its gears rapidly, releasing a burst of damaging energy in a 15-foot radius around it. Each creature in that area must make a DC 17 Dexterity saving throw, taking 28 (8d6) slashing damage on a failed save, or half as much damage on a successful one.

Temporal Stasis (1/Day). The guardian targets one creature it can see within 30 feet. That target must succeed on a DC 17 Wisdom saving throw or be paralyzed for 1 minute. The target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Defensive Matrix. When a creature the guardian can see targets it with an attack, the Clockwork Guardian can add 3 to its AC against that attack, potentially causing it to miss.