Pack Tactics.

The hound has advantage on attack rolls against a creature if at least one of the hound's allies is within 5 feet of the target and the ally doesn't have the incapacitated condition.

Supernatural Tracker.

The hound knows the distance to and direction of any creature that has come within 30 feet of it, even if that creature is on a different plane of existence. If the creature being tracked by the hound dies, the hound knows.

Actions

Bite.

Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 10 (2d6 + 3) piercing damage plus 3 (1d6) necrotic damage. If the target is a creature, it must succeed on a DC 13 Strength saving throw or have the prone condition.

Bonus Actions

Shadow Step (Recharge 4–6).

The hound magically teleports, along with any equipment it is wearing or carrying, up to 40 feet to an unoccupied space it can see.

Harrow Hound