Horcruxes; because of course it would come down to those. Two twinned shards of soul from the wrong bodies shoved down into the right hearts, an action that left them both panting, both cooling, their Lord standing above them with a smile on his face and bared amusement in his eyes, the twisting form of Nagini swaying side to side atop his shoulders as she observed them. It wasn’t painless, it wasn’t quick, but soon enough they had their ritual and their rewards.