Complex sentence: Not only does his name reference the God of Death, but death is a strong theme for Arumat's character as he refers to himself as death incarnate, due to the death of his comrades in the past and how he has killed many people in battle.
Split into simpler sentences: Not only does his name reference the God of Death, but death is a strong theme for Arumat's character. He refers to himself as death incarnate, due to the deaths of his comrades in the past and the many people he has killed in battle.