Weapons made out of alchemical silver bypass the damage reduction of lycanthropes and some Baatezu (ie, devils).
According to the entries here (Erinyes, Horned Devil, Pit fiend, Imp) alchemical silver weapons don't suffice, you also need a good aligned weapon (e.g. from the paladin spell Bless Weapon) to bypass the DR. If it weren't, the description should say "OR" and not "AND". Needs checking. GFallen (talk) 19:54, November 26, 2012 (UTC)