Auryn's Approximated Annihilation

You focus on a few positions, filling the material with the ability to magically explode.
Pick three spaces. Each of those spaces becomes embossed with the raw magic of this spell, creating an obvious glow from the floor in that space. As a bonus action, you can trigger the detonation for one, some or all of the spaces. You also choose one of five damage types: cold, fire, poison, acid or lightning.
When you trigger detonations, creatures on or within a 5ft radius of the chosen spaces must make a Dexterity saving throw. Creatures standing on the space take 10d4 of the chosen damage type on a failed save, or half as much on a successful one. Creatures standing in the 5ft radius of the space take 5d4 of the same type of damage on a failed save, or half as much on a successful one.~
At Higher Levels. When you cast this spell using a spell slot of 5th level or higher, you create an additional rune for each slot above 4th. The maximum for this is eight runes.