Bladethirst imbues an edged melee weapon with a +4 enhancement bonus to hit until the weapon strikes at least once. Upon a successful weapon strike, it "drinks" 2d8 points of damage + 1 point per caster level (maximum +10), storing them as either positive energy, if striking a living creature, or negative energy, if striking an undead creature. The same blade can then be used to channel the stored energy to a willing target through a non-lethal touch attack or to an unwilling target through a standard attack, healing or harming as usual in addition to dealing normal weapon damage. Any weapon bonus dissipates on the first successful strike during the duration of the spell and any unchanneled stored energy dissipates at the end of the spell's duration.