Thermal Detonator (Devastating)

Thermal detonators are unique in that can only be turned off by whoever turned them on. They can be set to detonate on impact or with a timer that causes them to explode on initiative count 20 (losing all initiative ties). As an action, you can prime and throw a grenade at a point you can see within 30 feet + your Strength modifier x 5. Each creature within 20 feet must make a DC 24 Dexterity saving throw. A creature takes 12d6 fire and 12d10 kinetic damage on a failed save, or half as much as on a successful one. Additionally, on a failed save, the creature is knocked prone.