You are the center of the universe. – Pulls nearby enemies towards the wearer when its shield charge is depleted. This can be helpful in getting second winds, provided shield depletion and getting downed occur in quick succession.
The Black Hole has the highest nova damage in the game, but the Flame of the Firehawk will release more novas in a short period of time, which may result in more total damage from the latter even if the damage of each nova is lesser
The Black Hole pulls enemies towards the wearer when fully depleted. This, combined with one of the highest nova damages in the game, makes it very helpful when fighting mobs.