The Goblin Sword 

Weapon short Sword (Very Rare Cursed Weapon) (Requires Attunement)

Description: The goblin sword is a short sword with rough square shapes built into the handle. The blade is slightly curved with jagged edges. While roughly made, the sword shines with a bright silver gleam.

The goblin sword grants a +3 bonus to attacks and damage but only in the hands of a goblin.

Goblin Curse: If anyone but a goblin picks up a goblin sword, the blade will cast Polymorph as if by a 10th level sorcerer (Wisdom saving throw DC 13) to transform the victim into a goblin. The sword can do this once per day. The transformation is permanent until the victim dies, the enchantment is dispelled, or the goblin sword is destroyed. The victim retains all of their class abilities, base ability scores, and equipment. However, their race is now considered goblin, they lose any racial abilities and their size becomes small. Also, their ability to speak common is replaced with the goblin language. The victim can still speak any other languages they know.

Removing the Curse: A victim of the goblin curse can be cured with a remove curse spell or any other 3rd level spell that can remove enchantments.

Destroying the Goblin Sword: A goblin sword can be destroyed by damaging it with a 6th level spell or higher. It can also be destroyed by tossing it in lava or by dragon fire.