Complex sentence: He was then killed in battle against Blade when Nomak actually pushes the blade of a sword further into himself, puncturing his heart and causing his death, to finally free himself from the pain his condition constantly causes him.
Split into simpler sentences: He was then killed in battle against Blade when Nomak actually pushes the blade of a sword further into himself, puncturing his heart and causing his death. This to finally free himself from the pain his condition constantly causes him.