Complex sentence: Morbius describes how one by one the rest of the expedition was killed by an unknown planetary force that vaporized their starship, the "Bellerophon", as the last survivors tried to lift off.
Split into simpler sentences: Morbius describes how one by one the rest of the expedition was killed by an unknown force. It finally vaporized their starship, the "Bellerophon", as the last survivors tried to lift off.