House of Hades

HI guys, 
I am rereading the Heroes of Olympus series, I have just finished the last book of the series called House of Hades all 583/583 pages. 
Here is a picture:

I have rereading the House of Hades book because it was so interesting and exiting the first time that I wanted to reread it in case that I had missed some details. 
The book is set in present day, they start of in the north of Rome and they continued through out the book to Greece with some stops on the way. 
In the book there goal is to get to Greece to the house of Hades where they will meet Percy and Annabeth who had fallen in to Tartarus. They will need Annabeth and Percy to survive there journey so they can close the does of death from the inside and the rest of the group will close the doors from the outside, that way when they kill a monster it will take a long time for it to reform and fight again. 
The word that was a bit unknown for me was: Akhhlys, she is the goddess of misery,poison. 

Anka