Source - Waterdeep: Dungeon of the Mad Mage

Wondrous Item, Rare

This twelve-sided metal die is 12 inches across and bears the numbers 1 through 12 engraved on its pentagonal sides. The dodecahedron contains arcane clockwork mechanisms that whir and click whenever the die is cast.
The dodecahedron can be hurled up to 60 feet as an action: A random magical effect occurs when the die comes to a rest after rolling across the ground for at least 10 feet. If an effect requires a target and no eligible target is within range, nothing happens. Spells cast by the dodecahedron require no components. Roll a d12 and consult the following table to determine the effect:

D12 Effect
1-2 The dodecahedron explodes and is destroyed. Each creature within 20 feet of the exploding die must make a DC 13 Dexterity saving throw, taking 40 (9d8) force damage on a failed save, or half as much damage on a successful one
3-4 The dodecahedron casts light on itself. The effect lasts until a creature touches the die
5-6 The dodecahedron casts Ray of Frost (+5 to hit) targeting a random creature within 60 feet that doesn't have total cover against the attack.
7-8 The dodecahedron casts Shocking Grasp (+5 to hit) on the next creature that touches it.
9-10 The dodecahedron casts Darkness on itself. The effect has a duration of 10 minutes.
11-12 The next creature to touch the dodecahedron gains 1d10 temporary hit points that last for 1 hour.