I don't see why it's so hard to get the difference on this one. You see, the expression "cannot take wounds" basically removes from the game altogether the possibility of assigning wounds to the Wraiths. It's WAY different from preventing wounds. If the wounds WERE simply prevented, then you'd be immune to archery fire, because you could assign all the archery wounds to the wraiths, when they'd then be prevented. However, since the possibility of wounding them is not present anymore, the archery fire will end up turning your Ring-bearer into a pincushion, since he'll most likely be your only character (or one of the few) that CAN have wounds assigned, so you WILL have to assign them to him. Since the text on the Tomb says that "wounds can't be prevented", it means that, once assigned, no effect may prevent them from being placed, ONCE ASSIGNED being the key part. Since you CAN'T assign them, the Tomb's text never actually takes place.