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.
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.
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.
When the Grim Harrow first found the faerie realm known as the Gardens of Delight, that place was home to a large population of blink dogs. The Undead invaders slaughtered the blink dogs and settled in the gardens, transforming the demiplane forever. In time, the necrotic magic of the Grim Harrow animated the corpses of the blink dogs as the first harrow hounds.