Tixan's Glacial Grenade

You transform the gemstone or crystal in your hand into a perfectly smooth glacial orb which speeds towards location of your choice. You can choose to aim this crystal at a single target or at a specific point in space. If aimed at a single target, you must make a ranged spell attack. Whether the crystal hits its target, misses, or was aimed at a point in space, as soon as it hits anything, it explodes. Each creature in 20 foot radius sphere must make a Dexterity saving throw. A target takes 8d8 cold damage on a failed save, or half as much damage on a successful one. After the explosion, dozen of ice shards begin to fly out past the sphere radius. Any creature 5 feet close to the sphere takes 3d4 piercing damage from the icicles.

At Higher Levels. When cast with a 6th level slot or higher, damage of the explosion increases by 1d8 for each level slot.