When you roll a 20 with this magic weapon, the target takes an extra 7 Bludgeoning damage.

Note: According to the SRD, it is an extra 2d6 Bludgeoning damage, although this is incorrect.

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.

Two-Handed

This weapon requires two hands to use. This property is relevant only when you attack with the weapon, not when you simply hold it.

This magic weapon deals an extra 2d6 damage to any creature it hits. This extra damage is of the same type as the weapon's normal damage.

Heavy

You have Disadvantage on attack rolls with a Heavy weapon if it's a Melee weapon and your Strength score isn't at least 13 or if it's a Ranged weapon and your Dexterity score isn't at least 13.

Two-Handed

A Two-Handed weapon requires two hands when you attack with it.

Mastery: Topple

If you hit a creature with this weapon, you can force the creature to make a Constitution saving throw (DC 8 plus the ability modifier used to make the attack roll and your Proficiency). On a failed save, the creature has the Prone condition.