Sling of Piercing weapon, uncommon (requires attunement)

As you swing this sling around your head you can hear it whistling, and the ammunition begins to glow a faint white.
This sling has 8 charges and regains 1d6+2 charges each day at dawn.

If you expend a charge when you make an attack with this weapon the ammunition screams forward in flash of light. You make a single attack roll against all targets in a 1-foot wide 60-foot long line. On a hit the target takes an additional 2d4 piercing damage.