Delayed Time Bomb

A bright streak of light flashes from your pointing finger to a point you choose within range and appears as a glowing bead for the duration. When this spell ends, either because you lost concentration or you end it, the bead blossoms with a low roar into a vortex. Each creature in  20 foot radius must make a Dexterity saving throw. On a failed save a creature takes the accumulated time damage, on a successful save they take half the damage. The spell’s base damage is 12d6. If at the end of your turn the bead has not yet detonated, it gains 1d6 damage. If a creature touches the bead, then they make a Dexterity saving throw. On a failed save the bead explodes, on a successful one the creature can throw the bead up to 40 feet. If the bead makes contact with an object after being thrown, it explodes.