Pyroconverger

From Guildmasters' Guide to Ravnica, page 180.

Description
Wondrous item, uncommon (requires attunement)

A Pyroconverger is an Izzet-made flamethrower. It carries a risk of malfunction each time you use it.

As an action, you can cause the Pyroconverger to project fire in a 10-foot cone. Each creature in that area must make a DC 13 Dexterity saving throw, taking 4d6 fire damage on a failed save, or half as much damage on a successful one.

Each time you use the Pyroconverger, roll a d10 and add the number of times you have used it since your last long rest. If the total is 11 or higher, the Pyroconverger malfunctions: you take 4d6 fire damage, and you can't use the Pyroconverger again until you finish a long rest.