Flechette Mag, Fragmentation (Devastating)

When triggered, this enhanced flechette cannon ammunition fires a volley of kinetic flechette rounds in a short line 15 feet long and 5 feet wide or a long line 45 feet long and 5 feet wide. A single flechette mag holds enough ammunition for three attacks in a short line or one attack in a long line. Each creature must make a DC 24 Dexterity saving throw. A creature takes 7d10 kinetic damage on a failed save, or half as much as on a successful one.