Amulet of Og

The Amulet of Og allows you to use a D20 for all rolls for 3 turns, except for attack rolls. For attack rolls, roll a D20 then roll a D6 dividing the d20s result by the d6s result for and it will equal the damage you will do (D20 divided by D6 = dmg). After 3 turns using the Amulet, roll a D20. If you get anything but a 20 the amulet vanishes in a blinding flash of light. If you get a 20, the amulet is not useable for 5 turns and then is usable once more for 3 turns, however it is destroyed no matter what after your next three turns of use.

Dont ask why it is called the amulet of og, its an inside joke