Complex sentence: Fortress snaps out of it to find himself on a roof in Chicago, before he can get his bearings, he sees Overt-Kill down in the street causing mass destruction while Youngblood arrive on the scene to face down Overt-Kill.
Split into simpler sentences: Fortress snaps out of it to find himself on a roof in Chicago, before he can get his bearings, he sees Overt-Kill down in the street causing mass destruction. Upon seeing Overt-Kill he see's Youngblood arrive on the scene to face down Overt-Kill.