Death is visited by Jedah Dohma, who proposes an alliance to achieve equilibrium between life and death on both their worlds. Needing the six Infinity Stones to do so, Death deceives Thanos and Ultron into aiding her, granting Thanos the Space Stone and sending Ultron to retrieve the Reality Stone from Abel City. Sigma intercepts Ultron, and the two forge an alliance. They betray the others and use the Space and Reality Stones to merge the two dimensions and fuse themselves into a single being named “Ultron Sigma”. To wipe out biological life, they begin unleashing an evolved form of the Sigma Virus that turns organic creatures into synthetic beings under their control. An alliance of heroes from both worlds is then formed. They manage to keep Ultron Sigma at a stalemate until they rescue Thanos from Ultron Sigma’s prison and secure him in a containment field at Avengers Tower. To gain their trust, Thanos reveals the locations of the remaining four Infinity Stones, and teams of heroes are dispatched to find them.