Flametongue Weapon - 0 mana
Adds your weapon damage as + Spell Damage to any damaging spell but causes 1 durability loss on the weapon each time it is used.
This would give +2 spell power since Shaman weapons are all two damage. The enchantment is tied to the weapon so once it losses all durability (or is oozed), the flametongue weapon is gone as well. Casting it twice on the same weapon would do nothing.