Luna's Blessing (Rank 4) Edit
When the moon is visible in the night sky, silver refuses to cause the Garou aggravated wounds. Indeed, if the moon waxes full, silver weapons may well turn on those who would wield them against the character. A Lune teaches this Gift.
For each strike against the Garou, the wielder of the weapon must roll three extra dice on the attack; these dice are read only to check for botches. The Garou can soak and regenerate silver as if it were bashing or lethal damage (depending on whether the silver is part of an edged weapon or not), but only when the moon is in a visible phase above the horizon. Therefore, the Garou is still vulnerable during a new moon.
Source: 3rd ed WWtA Corebook