This one has been my favorite of the "Heroes of Olympus" series thus far! Each of the characters had their own demons to battle, and I've loved watching each of them continue to develop. I can't wait to read the final installment in the series.

Hazel
Hazel has to be my favorite character within the "Heroes of Olympus" series. In "The House of Hades," I was rooting for her the entire time. When she was first able to control the Mist, I was elated. I thought she was going to die in the House of Hades, but she proved to be resilient, witty, and a fighter. Without her, they would not have been able to navigate the underground at all. She is a true leader.

Frank
Frank has to be the one that has the most character development thus far. I've enjoyed watching him change from shy and unconfident to the new praetor. I hope he embraces this role well and continues to grow in confidence.

Jason
Jason faced challenges throughout this series, but I can't help but root for the guy. He blew me away when making Frank praetor.

Piper
We didn't read as much from Piper's POV in this book, but she really had an impact throughout the story. From waking Festus with her charmspeak to learning sword fighting and using that during their battle in the House of Hades. She really has doubted herself too much since the beginning.

Leo
Leo played a huge role in "The House of Hades." I found him to be slightly annoying in "The Lost Hero," but he's really grown on me. His ability to think on his feet saved him multiple times throughout this book. I'm really hoping that he is able to someday reconnect with Calypso. It broke my heart when he sailed away with a crystal from her cave and the thought that she had fallen in love with him, too.

Percy
I first fell in love with Percy when reading PJO. I thought he was going to die in this book. I thought he was going to force Annabeth to go on without him so that he can close the Doors of Death from the Tartarus side, but alas, Bob and Damasen to the rescue. I like continuing to see Percy develop as a character. He realized that he hasn't been the best of friends to some of the people he has encountered, and I hope that he remembers that continuing with the series. Annabeth noticed a change in Percy when he began controlling some of the elements in Tartarus, so I'm curious to see how Tartarus has changed him.

Annabeth
Annabeth really went through in in the "Mark of Athena," and I really couldn't believe RR pushed her into Tartarus after following the mark of Athena! This poor girl has been through hell and back! In spite of that, she continues to be a strong, bad-ass, and I love her! I was glad to see her make it out of Tartarus alive.

Nico
I wish RR wrote chapters from Nico's POV. I know he isn't one of the seven of the quest, but I think that he would have some very unique insights. An ENTIRE book from Nico is a NEED!