Vicious Heavy Crossbow Ranged weapon (martial, heavy crossbow), rare. When you roll a 20 with this magic weapon, the target takes an extra 2d6 piercing damage. Ammunition. You can …

Longrifle: Heavy crossbow, double range increment. Amber Bracer: Worn on the wrist, can wield as light crossbow, deals force damage. Once per day when it hits, the wielder can cast hex on …

This heavy crossbow was specially crafted to take down the toughest of foes. Lord Dominik's Regards Martial Ranged Weapon (Heavy Crossbow), artifact (requires attunement) Giant …

Heavy. Creatures that are Small or Tiny have disadvantage on attack rolls with heavy weapons. A heavy weapon's size and bulk make it too large for a Small or Tiny creature to use effectively.

When you view a magic item while the Detect Magic spell is active, you'll see certain auras based on the schools of magic at work in the item. For a Vicious Heavy Crossbow, auras include:

Flaming Heavy Crossbow. Weapon (crossbow), very rare. You gain a +2 bonus to attack rolls with this weapon. On a hit, you do an additional 1d8 fire damage to the target.