Drums of Booming Thunder

A set of rhino-skin drums with 3 sizes. The drums are imbued with lightning energy, conducted through a magical crystal embedded into the rhino skin itself.

Boom of Thunder - You strike at the drums with fury, causing the drums to create a sonic boom that resembles thunder. All targets within 10 ft around you take 1d8 lightning damage and must pass a constitution saving throw of 10. If they fail, they are stunned for 1 turn.  The damage bonus increases as you level up, from 1d8 at level 1, 2d8 at level 5, 3d8 at level 10, 4d8 at level 15, and 5d8 at level 20.