Ao Hai's Fang (Patreon)

Weapon (longsword), legendary (requires attunement by a monk)

This ancient sword was forged in a kingdom ruled by a tyrannical dragon that has long since sunken to the bottom of the ocean. While attuned to Ao Hai's fang, you are proficient with it. You gain a +3 bonus to attack and damage rolls made with this magic weapon, which is a monk weapon for you.

Dragon King's Wrath. As a bonus action, you can spend 4 ki points to channel the fury of a powerful dragon and enter a magical rage. While raging in this way, you gain the following benefits:

• If you aren't wearing armor, dragon-like scales cover your body, granting you a +1 bonus to AC.
• You can't be charmed or frightened. 
• You can make one attack with this weapon as a bonus action on each of your turns, and when you use your Flurry of Blows, you can make two attacks with this weapon instead of two unarmed strikes.
• When a creature within 5 feet of you hits or misses you with an attack, you can use your reaction to make an attack with this weapon against that creature immediately after its attack.

This rage lasts for 1 minute and ends early if you are knocked unconscious. You can also end your rage on your turn as a bonus action. This property can't be used again until the next dawn.

Ships sank, people died, and countries burned. Nothing can compare to a dragon's rage.