"Well, the necromantic spells we'll have to use are pretty powerful," Luna explained. "You have to understand, Neville ... we'll be ripping a hole in the very fabric of existence ... in order to reach the Realm of the Dead. We will have to take a life in order to produce an energetic release potent enough to do that, and when the soul of the sacrifice crosses over to the other side, the portal they use will be forced to stay open by the enchantments on the Archway. The spells will summon forces from beyond the portal, too ... creating a cycle of renewing energy on the gateway that will be powerful enough to keep it in the open position for as long as we need it."