Summary: Slowly it was rebuilt from the same node, from the same tiny green spark that hovered at the core of the spell as he fed it power. Power not just to destroy the thing, but to destroy all things, all the things that made him old and feeble and slowly withered him away; all the things that crippled and pained him. And the words formed with the energies as he manipulated them, churning endlessly as they sought what they required to fulfil his bidding. Mimicking the languages of old, learning from those from which it grew until it had a purpose of its own. Avada Kedavra, I destroy as I speak.