Complex sentence: Shepard returns to the Citadel to request permission from the Council to pursue Saren, but Shepard's request is denied by the Council, who consider the existence of the Reapers too unclear to risk a war with the Terminus Systems.
Split into simpler sentences: Shepard returns to the Citadel and requests permission from the Council to pursue Saren. However, his request is denied by the Council, concerned of risking a war with the Terminus Systems.