It's so refreshing to see how close Thalassa and Aeras are. I'm glad Aeras didn't distance herself from her sister because of her condition or vice versa. Also, can Aeras fight as well? It sounded like she could when she told Thalassa that she should have stayed with her.

This is more of a personal preference but I think you could make your already good story even better with a little more description. Your chapters tend to be a little dialogue heavy. (I struggle with the same thing, honestly.)