As an action, a creature can light a stick of dynamite and throw it at a point up to 60 feet away. Each creature within 5 feet of that point must make a DC 12 Dexterity saving throw, taking 3d6 bludgeoning damage on a failed save, or half as much damage on a successful one.
A character can bind sticks of dynamite together so they explode at the same time. Each additional stick increases the damage by 1d6 (to a maximum of 10d6) and the burst radius by 5 feet (to a maximum of 20 feet).
Dynamite can be rigged with a longer fuse to explode after a set amount of time, usually 1 to 6 rounds. Roll initiative for the dynamite. After the set number of rounds goes by, the dynamite explodes on that initiative.