Arm of War (Warforged Component) (3.5e Equipment)
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This Arm can morph itself into a variety of weapons.
The forearm and hand of this magical Warforged limb may morph into a specific weapon (chosen during item creation) with a command thought from the Warforged it is attached to. It completely replaces the Warforged's arm, and as such requires a DC 25 Craft (armorsmithing or leatherworking) check and six hours to replace a limb with this one. Much like its companion item, the Eyes of War, this arm was usually bestowed upon high-ranking Warforged during the war (rare as they were). Unlike the Eyes, this item was imperfectly replicated from ancient relics found on Xen'drik, and was not successfully cloned until about a decade ago.
Aside from the "morph" property, most Arms of War are created nonmagical with respect to the weapon. As such, the cost to create one is the price of a masterwork version of the item (which must be commissioned to special requirements beforehand) plus 1k GP. An Arm of War can in theory contain any single one-handed weapon, even a masterwork battlefist (600gp) or a hand crossbow. Once the arm is crafted and attached, the weapon may be enchanted in much the same way as the warforged's armor plating.
If within an antimagic field or similar effect, an arm simply cannot morph between forms. For this reason, those few Warforged who go up against foes with antimagic find the battlefist model handy.
 Artifact Version
This is the version from Xen'drik that the more common versions are imitated from. These are considered lesser artifacts. For effective price, take the value of an equivalent "modern" Arm of War and add 2,500 GP.
This arm consists of two weapons, a special crossbow, and a melee weapon.
The crossbow behaves much like a standard light crossbow. However, the arm may hold up to five bolts at any time, which may be reloaded with a move action's worth of concentration to move the inner workings. The DM may opt to treat this as either reloading a crossbow normally or casting a level 0 spell for purposes of interrupting it. It is essentially a "lesser armbow", except that it uses regular ammunition.
The melee weapon can be anything, though it is usually a longsword, warhammer, or battleaxe. Battlefists are probably the next most common model.