Thear's Explosive Rune

A small, barely visible butterfly-shaped rune appears on a surface you touch. The rune is nearly invisible, requiring an Intelligence (Investigation) check against your spell save DC to find it.

When a creature gets within 5ft of the rune you can use your reaction to trigger the rune, causing it to explode, each creature within 5ft of the rune must make a Dexterity saving throw. On a failed save the creature takes 5d10 fire damage or half as much on a successful save. The explosion also deals damage to the surface the rune was placed on.

You can also use a bonus action to either trigger the rune or dispel it causing it to disappear harmlessly. Casting this spell while the rune exists will immediately dispel the old rune.