Alustin, called the Last Loyal Son of Helecote, is poised to get revenge on just about everyone when he detonates the Tongue Eater in Haveth City. He just has to get it there and keep everyone distracted while he does it. To that end he has assembled an army of Powers from Helicote's former allies. He has told them that The Last Echo of the Lord of Bells, the death curse promised by the Lich of Helicote as he died, will shatter Haveth City's defenses and that the Chitin Wand, stolen from Skyhold along with the Tongue Eater, will destroy the city if they can use it at the right spot. But Alustin has refused to tell them what the Last Echo is and failed to mention the Tongue Eater at all because these "allies" failed to come to Helicote's aid when the Dominion destroyed them. He too will die, but its worth it to get his revenge. There's just one minor problem. According to Kanderon as she "died", detonating the Tongue Eater won't just destroy Haveth City, it will destroy the entire continent. As the Haveth Dominion rallies their strongest Powers and Kanderon's allies race to stop Alustin everyone ends up in a dramatic three-way battle full of magic and chaos.

Hugh's world has been completely shattered. His teacher Alustin betrayed him and turned Hugh's pact with Kanderon into her downfall. He also stole the cruelest weapon their world has ever produced, the Tongue-Eater, which is capable of stealing a language and rendering its speakers mute for one or more generations. Sabae always suspected that they were a means to an end for Alustin, but not even she predicted his quest for revenge against the Empire would lead to such blatant treachery. With Kanderon presumed dead, and only one injured council member left, Skyhold is broken and leaderless. Hugh is convinced that Kanderon isn't dead and he is willing to do whatever it takes to help her, while his friends concoct a desperate plan to stop Alustin before he unleashes the Tongue-Eater. It's a plan that will literally expose them to multiple new worlds in the process.

Hugh and his friends survived the City of Ithos but Hugh was badly injured in the process. Kanderon's enemies are coming for her, the Splinter, and the Tongue-Eater, which she's had since she originally used the Splinter. She keeps it in the Skyhold Vault with the other things that should never be used. That is, after all, the true purpose of the Librarians Errant of Skyhold, to collect dangerous items and remove them from the world. Back at Skyhold they are preparing the defenses but with most of the Council killed by Bakori there is one wounded councilor, one admitted traitor, and Kanderon who has been gone dealing with Ithos. They may be weaker than usual but Kanderon built Skyhold with strong defenses and she has strengthened her alliance with the other Powers of the Erg desert even if many of them cannot leave their territories.

Sabae thought that Kanderon and Alustin used her and her friends as bait for the demon Bakori, but it turns out that Bakori was not really considered a serious threat. Kanderon and Alustin admit they were wrong about that but they were actually busy preparing for a far worse threat. Given that hundreds of students and most of Skyhold's powerful council died to Bakori, that's saying something. No one knows why the ancient Ithos Empire that once conquered the entire continent suddenly fell apart hundreds of years ago. It fell because they killed the mate and children of a young sphinx named Kanderon who then used her crystal and planar affinities to create what she calls the Splinter, which exiled the capitol of Ithos to a far distant world. She knew it wouldn't last forever but hoped the population would die before the Splinter ran out of power and the city returned. There's no way of knowing when it will reappear, but more than one faction wants to be there when it does. An Empire that opposes the Great Powers like Kanderon wants both the Splinter as well as the Ithos weapon known as the Tongue-Eater. Unfortunately Ithos poses a far greater danger than those powerful items. Kanderon later learned of a race known as the Cold Minds, that devour whole worlds in an effort to escape death. When Ithos returns there is a good chance it will bring the Cold Minds with it, and they devour whole worlds.

Hugo not only survived his summer travels with Alustin but stories of their accomplishments preceded them home to Skyhold. Thus, his fellow students have now dubbed Hugo "Stormward". Alustin is being cagey about the purpose of that trip but Sabae suspects that he used her and her fellow students as a cover to spy on the dragon Idris. There is no doubt that Alustin has been a remarkable help to Sabae, helping her make the most of her strange magic, so she is keeping her distrust to herself for now. Her doubts only grow when they get home and the four friends are tasked with ferreting out a traitor on the Skyhold Council. Kanderon has known for years that someone on the Council has been working against her but she was angered when the traitor made sure a vote to protect Hugo from Bakori, the demon in the labyrinth below Skyhold, went against Kanderon. The Council claims to believe Kanderon is exaggerating the danger to ensure an easy test for her "Pact"ed student, but she is certain this is a direct attack against Hugo because of their Pact. Hugo and his friends are uncertain how much help they can be, but except for Sabae, they trust Alustin and Kanderon implicitly.

The blurb for Into the Labyrinth is hardly unique; an awkward insecure student of magic must somehow find his talent before entering a monster filled maze at the year's end. This is really the story of four students, three of which have unusual parameters to their spellcasting, and their enigmatic mentor who is determined to turn those challenges into opportunities that will make them effective battlemages. In a multiverse world where most of the population has at least some magic, and every mage's abilities are unique based upon their affinities and casting style, the characters have more in common with the average superhero than Harry Potter or other "kids studying magic" books. Also, despite what the blurb says, the Labyrinth isn't the focus of the first book, which would be better described as the adventures of a young team of superheroes as they face epic villains, traitors, and mysterious named Powers, all while trying to avoid becoming the pawns of interplanar politics.