- “History is just an account of what supposedly happened, but it's rarely the full story, if ever.”
- ―Merlin to Team Trollhunters before conjuring the vision of the Battle of Killahead
The group is still trapped in Merlin's Tomb. Claire spots an opening, which they follow, though they're not certain it's a way out. Jim is reluctant to leave Draal, but Claire says Draal would want them to keep moving. They follow the path, but realize it doesn't seem to lead out. They follow a path to a room that has Merlin's body. The blue stone starts to glow. Jim takes it over to the body, where three lights exit the stone and enter Merlin's body. He wakes with a start. He's surprised to see that the Trollhunter is so young. Merlin gets up and asks about his Staff. They tell him they lost it to Gunmar. He says it's not the staff that's lost then. It's hope. Jim asks how he knew they'd come looking for him. He reveals says he's Jim's father. A few seconds later, he admits that he's kidding and says he can glimpse the future. He tells them he fought in the Battle of Killahead. Blinky and AAARRRGGHH!!! don't recall seeing him there. Merlin opens a window to the past.
They're transported back to the Battle of Killahead. They're at the moment when Deya the Deliverer delivered the decisive blow. As Blinky talks about fighting like there was no tomorrow, Claire spots his past self, fleeing from some goblins. Jim finds Draal and apologizes to him. Merlin then leads them to another area.
Angor Rot climbs his way back up to the top.
At Trollmarket, Gunmar shows off the Staff of Avalon. Soon, the Eternal Night will fall and with it, the world. In a nearby tomb, Morgana waits.
Claire's mother is worried their kids are dead. Barbara tries to stop the others from panicking, then excuses herself to the kitchen, where she eats some popcorn. Strickler comes in and tries to reassure her, but Claire's dad interrupts because the police are at the door.
Claire's dad takes Dictatious upstairs as they wonder why the police are there. They open the door to find Detective Scott passing out flyers for the Battle of the Bands. Before he can leave, he spots Dictatious, who falls down the stairs. He tries to radio it in, but Nana hits him with a shovel and knocks him out.
They hover over Detective Scott and watch him sleep. Nana says she has no regrets. They try to make a plan. Claire's mother suddenly has an idea.
Merlin takes them to where he was fighting directly with Morgana. None of the history books documented this, the true Battle of Killahead. She sowed the seeds of conflict between humans and trolls. The cost to stop Morgana was Merlin's magic. He had to expend all of his power to confine her for as long as possible. Now that's running out. They must battle again because of Gunmar.
Merlin closes the window to the past. It starts to rain in the cavern. Merlin says they need the power of the amulet to escape. Jim reveals that he destroyed it to get to Merlin. He hands Merlin the pieces. Merlin puts them down and then starts to put it back together.
As Scott wakes up, the other adults act out a trollhunting scene, pretending the trolls are in costumes. Scott applauds them. They tell him he passed out and pretend they were rehearsing a play called Trollfighters. Scott asks if there might be a part for him.
Merlin is still working as the situation gets worse. Merlin realizes a piece is missing. They use Claire's hairclip to fix it. As the water starts to flood in, Jim activates his amulet, the uses the Sword of Daylight to divert the water around them. He guides it to open a path to the outside. Merlin tells Jim he can do more than he realizes and he must help Merlin destroy Morgana.
Scott has joined the rehearsal. Barbara applauds his acting abilities and the others join in. Barbara sends Scott out with some script pages. Then he's gone and the others are relieved. They don't know how the kids do it. Barbara gets a text from Jim saying they're okay and they found Merlin.
Angor Rot confronts Gunmar for leaving him for dead. Gunmar says Angor Rot serves him and he will obey. After Gunmar is gone, Morgana speaks to Angor Rot, telling him to stay true and his devotion will be rewarded. If he wavers, she'll destroy him once and for all.
- Kelsey Grammer as Blinky
- Emile Hirsch as Jim Lake Jr.
- Charlie Saxton as Toby Domzalski
- Lexi Medrano as Claire Nuñez
- Jonathan Hyde as Mr. Strickler
- Fred Tatasciore as AAARRRGGHH!!!
- Ike Amadi as Angor Rot/Detective Scott
- David Bradley as Merlin
- Clancy Brown as Gunmar
- Mark Hamill as Dictatious
- Lena Headey as Morgana
- Tom Kenny as Javier Nuñez
- Amy Landecker as Barbara Lake
- James Purefoy as Kanjigar
- Andrea Navedo as Ophelia Nuñez
- Laraine Newman as Nana
- Victor Raider-Wexler as Vendel
- Matthew Waterson as Draal
- It is revealed that Merlin and Morgana participated in the Battle of Killahead, as Merlin explains that his battle with Morgana was the "true" Battle of Killahead. However, none of the trolls would ever recall seeing him nor Morgana during the battle.
- The famous quote from Star Wars The Empire Strikes Back is referenced when Merlin jokes to Jim about being his father.
- This is the first time we see Kanjigar the Courageous outside his Trollhunter Armor.