Fair enough. Adding in the bit about "open wounds" gives
Steal Blood (Su): A transient golem duplicate has an incorporeal touch attack that does 1 point of Constitution damage, it can literally reach inside a victim to sup upon their blood and life force, as long as that victim has unhealed hit point damage. Any open wounds the victim may have will instantly close and stop bleeding (this stops any continuing damage from a wounding weapon or the like). This attack is subtle and completely painless. The victim will not realize they have been attacked unless they succeed at a DC25 Spot check or a DC20 Autohypnosis check - they will notice any miraculously closed wounds, of course, but that appears to be healing rather than an attack. Another character who closely examines the victim can notice their anemia with a successful DC 20 Heal check.
A transient golem duplicate can also Steal Blood through any natural attacks possessed by the creature it has duplicated, adding 1 point of Constitution damage to each such attack that hits.
Transient golem duplicates must use Steal Blood to maintain their corporeal form. For every day they spend without stealing blood they will lose 1d3 points of Constitution. The duplicate can regain this lost Constitution using Steal Blood, regaining 1 point of Constitution for every point of Constitution damage it steals. If its Constitution should ever fall to zero it will immediately lose its transient golem duplicate template and Discorporate, becoming an incorporeal transient golem once more. The golem can not use Steal Blood to gain a Constitution score higher than the base creature it is duplicating, instead the creature gains 5 temporary hit points for every excess point of Constitution damage it steals, to a maximum equal to the bonus hit points of a Construct of its size. (e.g. a Medium-sized duplicate can gain up to 20 temporary hit points through excess Blood Stealing.)