Arrow Trap Rune

You draw a rune onto or into a surface, and it turns invisible after the rune is completed. The rune activates if you use your bonus action to trigger it or when a hostile creature comes with in 10 feet of the rune. When the creature come in range of the rune it will automatically detonate unless you use your reaction to make it hold. When it is triggered it shots out a spectral arrow toward the nearest target. The target creature must make a dexterity saving throw, on a failed save it takes 3d6 piercing damage, and on a successful save it takes half damage. To trigger the trap is a bonus action and its range increases by 10 feet when manually triggered.

At Higher Levels the rune shoot out an additional arrow per spell slot above 1st level.