Thermal Detonation

You touch a nonmagic, nonliving object no bigger than one cubic foot. That object, upon activation, will detonate. Spending an hour to prepare the object requires the gem. Taking an action to detonate the object requires the piece of jewelry to be worn or held. The spell deals cold/fire damage based on the detonation component.

The detonation deals 5d12+20 bludgeoning damage to any creature within 15 feet, and 4d8+10 cold/fire damage to any creature within 20 feet. All creatures within the blast are pushed back 15 feet, in a direction opposite of the center of the blast, and must make a dexterity save versus your spell save DC or be forced prone. Every creature within the blast must make a constitution saving throw versus your spell save DC. Upon a success, that creature takes half as much cold/fire damage.

The object and/or detonator can be identified using detect magic cast with a spell slot equal to or higher that the slot used to cast Thermal Detonation on the object, and can only be dispelled in a similar manner.

For every spell slot greater than 5, the bludgeoning damage increases by 1d12+5 and gains 5 feet of range. The cold/fire damage increases by 1d8+5, and gains 10 feet of range.