Banebolts of Eryxia

When you select this Relic, select one bolt weapon (see Codex: Space Marines) the bearer is equipped with. When that model is chosen to shoot with, if it does not fire special-issue ammunition (pg 50), you can choose for that weapon to fire a Banebolt of Eryxia. If you do, you can only make one attack with that weapon, but that attack has a Strength characteristic of 6, an AP characteristic of -2 and a Damage of 3.