Complex sentence: Rupert appears ruthless and sometimes cold-blooded as he is driven by a fanatical hatred of demons because one of them murdered his wife but he is a warm-hearted individual who cares about his friends and looks on Luke as a son.
Split into simpler sentences: Rupert appears ruthless and sometimes cold-blooded, as he is driven by a fanatical hatred of demons because one of them murdered his wife. However, he is a warm-hearted individual who cares about his friends and looks on Luke as a son.