You scribe runes of dire power on a single missile or thrown weapon (usually an arrow, bolt, dart, javelin, or spear), changing the weapon into a sinister missile of cold, enhanced bone.
When thrown or fired at a creature as a normal ranged attack, the weapon gains a +4 enhancement bonus on attack rolls and damage rolls.
In addition, any living creature struck by an arrow of bone must succeed on a Fortitude save or be instantly slain.
A creature that makes its save instead takes 3d6 points of damage +1 point per caster level.
Regardless of whether the attack hits, the magic of the arrow of bone is discharged by the attack, and the missile is destroyed.