The Old Die is a Pre-Hardmode accessory that can be purchased from the Bandit for 40 at any time. When equipped, the random damage deviation of each attack is increased. The minimum damage that can be rolled is -25% damage and the highest damage that can be rolled is +30% damage instead of the ±15% damage deviation that vanilla Terraria has. This means that non-rogue attacks deal 2.5% more damage on average.
If the player is holding a rogue weapon or wearing a rogue armor, the damage roll is rolled twice, with the higher damage value of the two becoming the damage increase applied to the weapon. This means that rogue attacks deal 11.66% more damage on average.