Mild Spoilers Below. Major spoilers will be hidden 
 4.5 stars. This series ended on a high note. I learn so much from reading Rick's books. I love mythology, and these stories are both entertaining and knowledgeable. We pick up where we left off. Loki has escaped and Magnus and co. must sail through the nine worlds to stop Loki from beginning Ragnarok, aka the Apocalypse with a capital A. They come up with the most ridiculous plan for capturing Loki, and go through a lot of trouble just to get the necessary pieces to execute said plan. Shit goes down, some of them are confronted by their past, and madness ensues. 
 Rick truly has a way work characters. Many times supporting characters won't be as fleshed out as the main characters, but not in this case. We learn about TJ and Mallory, specifically the nature of their deaths. We visit Halfborn Gunderson's hometown, and we return to Alfheim for Hearth's unfinished business. Sam and Alex grow as well with both of them dealing with Loki. Don't get me wrong Rick puts in his trademark humor, but he deals with important stuff as well. 
 Let's talk relationships. ALEX AND MAGNUS KISS TWICE! I love their romance. This is the first series I've read that has a gender fluid character, and I love it. For the second kiss there's a moment where Alex is a boy, and Magnus is like "huh, I just kissed a boy," but he doesn't care because it's Alex. Does that make Magnus bi? I'm not sure, but at the very least he's queer. Representation is so important, and it's so rare in fantasy and middle grade that I have to congratulate Rick for helping to normalize LGBTQ+ in media because it is normal. Biltzstone is not canon, but maybe that is something that will be addressed at a later time. Something tells me we haven't seen the last of Magnus and co. And of course, Sam and Ahmed are adorable as ever. Mallory and Halfborn Gunderson kiss and make up. All is well with our ships. 
 And yes, Percy and Annabeth do make a brief appearance in the beginning. It involves helping Magnus run a ship. But also, what was up with that cryptic phone call????? Annabeth was crying which tells me that someone fucking DIED, or at least something awful happened. I'm trying to remember if it was in The Dark Prophecy, or if this book simultaneously takes place with what will happen in The Burning Maze. Now I have to look it up to double check. 
 Overall, a great ending to a very weird trilogy. Out of all of the mythology Rick has written about, Norse is definitely the strangest. More than anything, this was a book about family and what that means to people. I hope we will see more of Magnus because there's so much more to explore.