Blade of Endless Strength (5e Equipment)
From D&D Wiki
Weapon (dagger), One of a kind (requires attunement)
The blade of endless strength is a deceptive seeming dagger, wrought with obsidian and silvery metal. According to legend, it was made by one of the first peoples who learned how to practice magic and crafting. It was designed to attune to the physical strength of the user. The stronger the user, the sharper the blade becomes.
Endless Death This blade attunes to the wielder's strength. This dagger's base damage is 2d4 if the wielder is below 5th level, 3d4 if the wielder is 5th-10th level, 4d4 if the wielder is 11th-16th level, and 5d4 if the wielder is 17th level or higher. In addition, the wielder may add 1/5th of their level (rounded up) to the attack and damage rolls.