Complex sentence: Dormammu captures Clea, and overpowers and imprisons Strange, but after the sorcerer manipulates Umar to free him, and then surprises Dormammu by pushing him through a portal to the Earth.
Split into simpler sentences: Dormammu captures Clea, and overpowers and imprisons Strange. The sorcerer manipulates Umar into free him, and then surprises Dormammu by pushing him through a portal to the Earth.