Clockwork Ironwood Hound

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

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

Magic Weapons. The clockwork’s weapon attacks are magical.

Relentless Tracker.  The clockwork knows the direction and distance to its prey, even if that target and the clockwork are on different planes of existence.  If the creature being tracked dies, the clockwork knows.

Unusual Nature.  The clockwork doesn't require air, food, drink or sleep.

Multiattack. The clockwork makes three attacks: one with its bite and two with its claw.

Bite. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 15 (2d10 + 4) piercing damage.

Claw. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 13 (2d8 + 4) slashing damage.

Booming Bark (Recharge 5–6). The clockwork emits a loud bark in a 30-foot cone. Each creature in that area must make a DC 16 Constitution saving throw. On a failed save, a creature takes 11 (2d10) thunder damage, and is stunned until the end of their next turn. On a successful save, a creature takes half as much damage and is not stunned.

Plane Shift (1/Day).  The clockwork casts plane shift, requiring no material components and using Intelligence as the spellcasting ability.  The clockwork can cast the spell normally, or it can cast the spell on an unwilling creature it can touch.  If using the later option, the targeted creature must succeed on a DC 16 Charisma saving throw or be teleported with the clockwork.