Complex sentence: Marica has already felt the power of Lord Ram (as mentioned in Baal Kaand) and is apprehensive, however, he thinks that he is going to die either way since Ravana will kill him through rage for refusing him.
Split into simpler sentences: Marica has already felt the power of Lord Ram (as mentioned in Baal Kaand) and is apprehensive. However, he figures that he is going to die either way since Ravana will kill him through rage for refusing him.