Seawrack Longsword

Weapon (longsword), very rare (requires attunement)

Lore. During the Divine War, certain wrack dragons created special weapons and equipment for their lieutenants. In so doing, they imbued the weapons with some properties of their elemental wrack. It is said that some of these items, especially the weapons, are sentient, and are as thoroughly evil as their creators.

Powers. You have a +2 bonus to hit and damage rolls you make with this magic weapon, and while you wield it you have resistance to acid damage. In addition, you can use a bonus action to speak sword’s command word, causing deadly acid to drip from it. While the sword drips acid, it deals an extra 2d6 acid damage to any target it hits. The acid lasts until you use a bonus action to speak the command word again or until you drop the sword. Finally, when you score a critical hit with it the target must make a DC 16 Strength saving throw or be forced prone.