Silver

Silver, Alchemical: A complex process involving metallurgy and alchemy can bond silver to a weapon made of steel so that it bypasses the damage reduction of creatures such as Devils and certain Undead like Vampires.

Silver weapons have 2 points lower hardness then equivalent steel weapons, and as such aren't quite as durable.

Silver weapons can bypass the damage reductions of Vampires, Lycanthropes and some Devils. With some devils (Pit Fiends and Horned Devils), the Good damage type may also be needed. (See Monster DR and weaknesses for specifics.) Since the Menace of the Underdark expansion, Lycanthropes exist in DDO with the introduction of Werewolf monsters.

Monks with the Shintao Monk III enhancement can bypass Silver damage reduction with unarmed attacks.

Silver ranged weapons, such as the Silver Slinger repeating heavy crossbow and Bow of the Silver Flame longbow, imbue their shots with the Silver damage type. The same is true of Metalline bows and crossbows. The Silver Longbow, despite its name, does not have the Silver damage type; it's simply a material type for the bow.

Any ranged weapon with Silver ammunition will bypass Silver DR. (This includes the Silver Longbow.)

Blessed Silver weapons
Available in in game store and can be crafted using Cannith Crafting.

Blessed Silver weapons are considered Good and overcome the damage reduction of most fey creatures like Dryads or Satyrs AND the damage reduction of most Lycanthropes like Werewolfs along with certain Undead like Vampires.

History
In the original release of DDO, silver weapons worked more like their pen and paper counterparts and dealt 1 point less damage per swing. This was changed to simplify the game.