Complex sentence: While Mytho's true personality does try to fight back against the corruption, as it progresses he becomes increasingly unstable and verbally abusive to Rue, but with her help he overcomes The Raven's blood when the last heart shard is returned.
Split into simpler sentences: While Mytho's true personality does try to fight back against the corruption, as it progresses he becomes increasingly unstable and verbally abusive to Rue. In the end however, with her help he overcomes The Raven's blood when the last heart shard is returned.