Gravity Bomb Spell

Gravity Bomb Spell:

Cost: 100,000 coins
Production Time: 45 minutes

Creates a large black ball. All troops and defenses in range will start attacking it for 5 seconds. At the end of the 5 seconds, a flying, larger version of the Wallbreaker will carry it to the middle of the base. Once he drops it, the bomb will do the amount of damage inflicted by troops onto the ball to all enemy troops, heroes, and towers within a 5 unit radius.

The Wallbreaker has these stats. If the towers can kill it before reaching the middle, then the ball will disappear.
HP: 300
Movement Speed: 15

If it seems like a good idea, I'll make the upgrade stats.