Giantcraft Ambusher

This dark metal axe contains the brute force of a fire giant inside and requires a Strength of 15 or higher in order to wield it. You gain a +1 bonus to attack and damage rolls made with this magic weapon. While holding the weapon, you can speak its command word using a bonus action to magically enlarge it. When you do, the weapon grows to three times its normal size until the start of your next turn. While enlarged, this axe has the reach property and deals an extra 2d12 slashing damage to any target it hits. The axe's weight doesn't change. While the axe is enlarged, it doesn't impose disadvantage on your attack rolls due to its larger size. Once this property of the axe has been used, it can't be used again until the next dawn.

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 when you attack with it.

Proficiency: martial, greataxe Source: The Griffon's Saddlebag: Book Two p. 88 (Third Party)