Arrow of Bone (EFA - A)

You scribe necromantic runes onto a thrown weapon or piece of ammunition during a long, grueling ritual. As you complete the spell, the item magically transforms into an identical item made of bone, and the runes glow with dark magic

For the duration, the weapon or piece of ammunition gains a +3 bonus to attack and damage rolls made with it. In addition, a living creature hit by the weapon or piece of ammunition must make a Constitution saving throw. On a failed save it instantly dies, and takes 8d8 necrotic damage on a successful one.

Regardless of whether the attack hits or misses, the magic is discharged by the attack and the missile is destroyed.