After a long battle in a ruined London, Shepard determinedly makes it to the Citadel beam after being greatly wounded by Harbinger, the most powerful Reaper. He/she finds Anderson being held hostage by the Illusive Man, who is either killed by Shepard or commits suicide if convinced of his indoctrination. The conflict ends in Anderson's death, after which Shepard is transported to the pinnacle of the Citadel. A childlike AI appears, proclaiming itself the Catalyst and the creator of the Reapers. It reveals that the Reapers harvest and preserve organics advanced by synthetics to allow more primitive species to evolve. The Catalyst concedes defeat to Shepard and gives him/her three ways to activate the Crucible: destroy the Reapers and all synthetic life, seize control of the Reapers, or synthesize organic and synthetic life together. The activation results in Shepard's death and the mass relay network being destroyed. However, if Shepard destroys the Reapers with a high enough Effective Military Strength (EMS), he/she will instead take a gasping breath from within a pile of rubble and survive.