"Machete" by Bob Greyvenstein
*Blade of Escalation first appeared in the 5e Campaign Setting Adventurer's Agency.
Blade of Escalation
Weapon (any sword), rare (requires attunement)
This sword, imbued with magical power by grandmaster weaponsmiths of Blumont, is perennially sharp, never requiring a whetstone. For each successful attack, the damage of the weapon increases by one additional damage dice of the weapon's type. The total number of damage dice rolled can never exceed four, regardless of the number of successive hits. On a miss, the sword's next successful attack strikes with one damage dice.