Complex sentence: In the alternate timeline of the "Flashpoint" event, Evan McCulloch is imprisoned in the mirrors called the mirrorverse, it is mostly assumed Citizen Cold killed him, and cannot leave the mirrors or he will die.
Split into simpler sentences: In the alternate timeline of the "Flashpoint" event, Evan McCulloch is imprisoned in the mirrors called the mirrorverse. It is mostly assumed Citizen Cold killed him, and he cannot leave the mirrors or he will die.