Personal Ballista

Weapon (heavy crossbow), very rare (requires attunement by a creature with 16 Strength or higher)

Made from specially enchanted wood, this massive crossbow packs the siege power of a ballista into a more manageable form. This crossbow can only be drawn while attuned to it. When you make a ranged attack with this magic weapon, you add your Strength modifier instead of your Dexterity modifier for the attack and damage rolls.

When you draw this crossbow without providing ammunition, it magically fabricates its own bolts. When the crossbow is loaded with these fabricated bolts, it deals an extra 2d8 bludgeoning damage on a hit and deals double damage to objects and structures. If the target is a Large or smaller creature, it must succeed on a DC 15 Strength saving throw or be knocked prone