- “You, my friends, are about to be the first Akiridions inside Trollmarket!”
- ―Toby to Aja and Krel
After learning the location of Gaylen's Core, Toby calls Trollhunter Jim Lake, and Blinky advises the royals to consult the Soothscryer.
After learning that the king and queen entrusted Kanjigar to protect Gaylen's Core from the wrong hands, Aja and Krel contact Trollhunter, Jim Lake Jr., and his mentor, Blinky, who advise them to venture to Heartstone Trollmarket before Morando does.
Aja and Krel monitor their parents as they race in the taco truck to beat Morando to Stuart's home. Varvatos feels Stuart's driving too slow and forces him to floor it. Aja tries rousing her parents, telling them they're on Earth. They arrive and stop.
Toby is editing film footage when Krel and Aja come in and hook up their parents' stasis chambers to the Daxial Array. Toby isn't happy that they'll be leaving soon to go home, insisting that Kleb or Alive will be debuting at the local Arcadia drive-in theater. Aja reminds him and Krel that they need to beat Morando to Gaylen's core first. Stuart tells them the story of Gaylen and how his core contains the power of a god. Aja and Krel tell Toby they need to find a troll named "Can-in-jars". He realizes they mean Kanjigar and calls Jim for them. Blinky comes on the screen mid-battle, telling them that they have bad timing, as he and Jim are below Hoboken, New Jersey battling against a mysterious armored foe. Briefly intimidated by the mystery knight, Toby quickly composes himself to re-introduce the Tarrons to his friends, but Blinky insists that they have to stay focused on the fight. Toby asks him if he knows where Kanjigar hid Gaylen's core. Blinky responds that Kanjigar kept many secrets but when Aja mentions that her parents bequeathed the artifact to both Kanjigar and Vendel, he advises they consult the Soothscryer before the call cuts out. Fortuitously, Toby knows where to find the Soothscryer: Trollmarket.
At Area 49-B, Kubritz shows Morando footage of the Eternal Night War, mentioning that her predecessor called the world of trolls, the Underneath, which is likely where Trollmarket is. In exchange for that information, he gives her body armor to wear.
Gathering his friends below the Arcadia bridge, Toby uses his horngazel to awkwardly trace the entryway to Trollmarket. Behind them, Morando and his Omens appear. They quickly enter Trollmarket and close the door behind them. Morando orders his blanks to break through the wall, but the barrier proves impenetrable, disrupting the traffic on the topside of the bridge. Unperturbed, he has them aim at the ground instead.
Making their way down the crystal staircase, Toby remains confident Morando can't get in. He then introduces the Akiridions to Heartstone Trollmarket, only to recoil in horror upon seeing the once spectacular troll civilization reduced to a dark, empty place. Seeing AAARRRGGHH!!! depressed seeing his home in such a state, Aja and Krel sympathize with him, reminding that at least Jim, Blinky and the trolls are safe.
Feeling their enemy ready to breach from above and with ominous noises all around, they make their way through to the Hero's Forge. AAARRRGGHH!!! clears the debris for Krel to step on the triggers to raise the Soothscryer. Aja and Krel each prepare to stick an arm in, but it stops spinning and emits a strange sound. An orb comes out instead. It pushes Krel toward The Deep. Toby tells them that going down there means facing your worst fear. Krel offers to go alone while the others stays behind to hold off whatever's coming. He takes the hoverboard into The Deep. Krel runs into a wall while following the light and falls.
Back in the Forge, it is not Morando and his Omens that emerge from the entrance, but Gumm-Gumms, which had become zombies from the dead Heartstone. Aja comments they smell worse than Stuart.
Krel, in human form, sits on a bench. People around town greet him. He hears his parents and learns that Earth is their home now. Just then, Morando's ships fill the sky and Morando takes the place of his parents, telling him there's nowhere to run and he'll destroy everything Krel loves. He watches in horror as the ships fire on everyone and everything in town. Morando himself pulls a weapon on Krel. Krel starts crying for his friends and family. Then he becomes determined and says this is his home, so he won't let Morando do this. He and Morando fight and stabs him while lying he's not afraid. Morando pixelates and disappears along with all his other surroundings. Krel realizes he did it.
The team is still fighting Gumm-Gumms when Morando and his blanks approach. AAARRRGGHH!!! throws a Gumm-Gumm, causing a cave-in that blocks Morando and his blanks. Varvatos sends Aja and Toby down to help Krel. Morando and his blanks come through to face Varvatos and AAARRRGGHH!!!
Krel is trying to get through a door when Aja and Toby arrive. Krel tells Aja what his worst fear was, what Morando will make reality if he gets Gaylen's Core.
AAARRRGGHH!!! runs away while Varvatos fights. Varvatos loses his weapon and Morando declares him guilty of treason, punishable by death. Varvatos says Morando will never be his king, grabs his leg, and throws him. AAARRRGGHH!!! says they need to jump and then throws Varvatos into The Deep, jumping himself right after. Toby is glad to see AAARRRGGHH!!! Krel tells them he hasn't been able to get the door open. Suddenly, the door lights up. There's a code. Part of it is in Akiridion, but Aja doesn't know the other language. AAARRGGHH!!! says it's Trollish and reads it with Aja and Krel's help. The whole door lights up when they finish and it opens as Morando and his blanks approach. They enter the room. A blank tries to follow, but Aja kicks it back and the door closes.
The light appears again and forms a hologram of a planet held in the palm of a hand, then into Gaylen himself facing Seklos. Kanjigar then appears to let them know the legend didn't end there. He built the room they're in to guard Gaylen's core for when House Terron would return someday. Aja and Krel introduce themselves. He tells them the core is theirs as it always has been. He gestures and Gaylen's core reforms. He tells them the core is now theirs to protect. They approach the top, but are knocked down when Morando comes in with this blanks. A battle starts between them and AAARRRGGHH!!!, Toby, and Varvatos while Aja and Krel climb to get to the core. Morando ignores the fighting and goes for the core himself. Krel knocks him down while Aja continues to climb. Morndo then grabs him and drop him down. Morando goes head-to-head with Aja. Morando reaches the core, but Aja grabs him. He holds her against a rock, so Toby comes up with his hammer and knocks Morando away. The structure starts to break, leaving Aja up against Morando to get to the core. The core falls when the blanks fire on it. One of the blanks picks it up as rocks fall around them.
Aja wakes up and learns that Morando got away with the core. They're all okay, but now the universe isn't.
- Tatiana Maslany as Aja Tarron/Queen Coranda
- Diego Luna as Krel Tarron
- Nick Offerman as Varvatos Vex
- Alon Abutbul as General Morando
- Uzo Aduba as Colonel Kubritz
- Rodrigo Blaas as Gnome Chompsky
- Nick Frost as Stuart
- Andy Garcia as King Fialkov
- Kelsey Grammer as Blinky
- Emile Hirsch as Jim Lake Jr.
- Laraine Newman as Nana/Miss Janeth
- James Purefoy as Kanjigar
- Cole Sand as Eli Pepperjack
- Charlie Saxton as Toby Domzalski
- J.B. Smoove as Phil
- Fred Tatasciore as AAARRRGGHH!!!
- Reginald VelJohnson as Jerry
- Frank Welker as Luug
- Thomas F. Wilson as Coach Lawrence
- Bebe Wood as Shannon Longhannon
- Steven Yeun as Steve Palchuk
- This is the first (and only) appearance of Heartstone Trollmarket in 3Below.
- This episode also marks Blinky and Jim's only physical appearance in Part Two of 3Below.
- There is a book entitled A Brief Recapitulation of Akiridion Lore, similar to A Brief Recapitulation of Troll Lore. Toby lampshades this by exclaiming "What? You guys have one of these, too?"
- Krel's worst fear is Morando destroying Arcadia and all of the friends he's made there. Toby's (before his nana giving him kisses, as revealed in "Where Is My Mind?") is dieting.
- Toby (along with Aja) drifting down into the Deep along with his Warhammer is a possible allusion to Mary Poppins.
- Running Gag: Varvatos giving Krel, Aja, and Toby "incentives" by shoving/throwing them into the Deep. Later, AAARRRGGHH!!! gives him an "incentive" and tosses him over the Deep before following suit.