Ensilvering Ammunition (5e Equipment)
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Weapon (any ammunition), uncommon (+0), rare (+1), or very rare (+2)
This piece of magic ammunition can disrupt the powers of a werecreature that it strikes. A lycanthrope hit by a piece of magic silver ammunition immediately reverts to its true form, and remains in that form for 1 minute. In addition, the lycanthrope must make a DC 15 Constitution saving throw. On a failed save, the creature loses its damage immunity to nonmagical weapons that aren't silvered. It may repeat the saving throw at the end of each of its turns to end this effect.
You have a bonus to attack and damage rolls with the rare and very rare forms of silver ammunition. Once it has hit a target, the ammunition is no longer magical.