Nightfall has come and we see the humans are battleing against the gumm-gumms army.

We now see Jim is struggling to fight off a gumm-gumm without his sword.

Claire: Heads up!

Fortunately Claire teleported and kicks the gumm-gumm away from Jim.

Jim: Just in the nick of time.

Jim does his best to fight but the shard on his chest weakens him.

Claire: We're getting through this together.

Douxie uses his magic to pin the gumm-gumm in mid air for Archie arrives and breathes fire against the gumm-gumms

Douxie: Ha, ha! Always hated those twits.

The gumm-gumms surrounded YN and Toph who are back to back until they exchange nods. Toph slam the ground to cause a rumble to force the gumm-gumms fall down before YN release his lava bending to let it finish off the gumm-gumms.

Toph: You fight well, pebbles.

YN: Learn from the best.

Arthur: Fight on! The day isn't over yet!

Soon the king notice someone appear from the sky and it was his sister in her golden armor.

Morgana: Night has already fallen. Elemen-zath!

Morgana unleash her magic to fight against the knights.

Douxie: Morgana's returned! She's enemy number one!

Jim: Go! We'll hold the bridge!

Merlin: Hisirdoux, with me!

The wizards goes after Morgana who went to the dark woods before they're at the middle of the woods.

Douxie: I feel dark magic.

Merlin: It means she's close.

Morgana: (Chuckles.) An old man and a foolish boy, lost as always. Do you dare run or face my vengeance?

Archie: Um, is there a third option?

Before they could do anything, Morgana uses her magic vines to trap them to the ground as they struggle to break free until one of the vines wounded Merlin badly.

Merlin: Hisirdoux, run!

Fortunately, Douxie manage to break free and attacks Morgana. But she just left the woods. Fortunately this gave him the opportunity to help Merlin up after breaking him out of the vines.

Douxie: Merlin! You're injured! Badly.

Merlin: (Groans.) Hisirdoux, if I should fall this day...

Merlin hands the scroll to Douxie who checks and reads it.

Archie: "Heart of Avalon"?

Douxie: "Building a tomb"? Why are you giving me this?

Merlin: Foreseeing the future means preparing for the worst of it, including your wounded friend.

Douxie: Jim? What about him?

Merlin: The corruption in his heart has no cure. When he returns to the future, it will overtake him.

Douxie: No! No, there must be some other way. I made a promise to them, to Claire, to get them home alive, all of them!

Merlin: Yet, to save time itself, you all must return home, even if it means James Lake will be no more.

Douxie sigh before they continue onwards to hunt down Morgana as Merlin speaks.

Merlin: Such is the burden of a wizard--
to make the hard choices mortals cannot. Now it is yours to bear.

Soon the arrive to what appears to be the gumm-gumms lair. They continue onwards.

Merlin: Morgana, reveal thyself!

She does so and teleported at a distance.

Morgana: Look what has wandered into my web.

Merlin: These are dark powers you meddle with, Morgana. Who granted them? Who resurrected you from death?

Morgana: Wizards beyond your ken. You three aren't going anywhere. I have a king to slay.

Morgana created a clone of herself with magic construct to keep them busy while she alone leaves to kill her brother. Back in the battle, Gunmar takes down most of the knights while his son fights off Lancelot and Arthur faces Gunmar.

Arthur: Gunmar, you have terrorized this realm for too long! It ends here!

Gunmar: You cannot win, little king! The surface lands belong to my kind!

They both clash their weapons but Gunmar overpowered him enough to knock the king back.

Arthur: Nimue, grant me a blessing to strike down this tyrant.

Arthur granted enough strength to strike Gunmar back with the power of the Excalibur.

Arthur:  Your reign of terror is over.

Before he could get the chance to end Gunmar, the arcane order join the battle which shock the future team to see them here.

Claire: The Arcane Order? They're here?

YN: Definitely not good.

Galahad: We may have come to the end of days! Charge!

The knights tries to fight the arcane order but they were to powerful. To make matter worst, Morgana returns to the battlefield to face her brother.

Morgana: Brother! We have some unresolved issues.

Arthur: Sister? You're alive?

She attacks the king with her magic.

Arthur: Stop this! Our blood is the same.

Morgana: Is that so? Then let's spill some of yours and make sure!

Lancelot does his best to fight off Bular but he was about to be overpower by Bular. Steve tries to help, but the gumm-gumms were in his way.

Steve: Lancelot! No!

Lancelot: Courage, Sir Steve. Carry on my banner, friend...Fight on for honor.

Bular then ended Lancelot with his blade.

Steve: No!

Steve rage gave him strength and fight off the gumm-gumms before faces Bular.

Steve: Die, creeper!

He yells until he realize he won't stand a chance against Bular. Having no choice but to run away from Bular.

Bular: Coward!

The arcane order fights off the humans easily since they uses elements against them.

YN: Those arcane order will bring down our numbers unless we do something.

Jim: No way, they're too powerful for you alone.

Claire: They'll kill you if you do!

YN: They can try.

YN charges at Skrael after creating his stone armor. But Skrael freezes YN and traps him in ice. However, this was planning as YN uses his lava bending on the outside of his stone armor while the inside protected him from burning. With that, he manage to break free from the ice which shocked Skrael.

YN: Never faced a lava bender before? Cuz you're about to.

YN created more lava and uses it against Skrael.

Meanwhile Morgana continue to use her magic against Arthur until he gives up.

Arthur: You were right...It is like you said....

The king drop his sword as he now see the truth.

Arthur: We are all the same...I have wronged you, as I have all creatures in my realm. I now fight to save them from the violence I have sown.

Arthur: This carnage, these deaths, we can end this.

Morgana: This...This is a lie. A trick!

Arthur: No, this is our redemption.

This gave Morgana hope from her brother.

Arthur: I should have listened to you.

Before he could hug his sister, Bellroc appear behind him.

Morgana: Brother!

Arthur scream when Bellroc stabbed him from behind.

Morgana: No!

Bellroc: Merlin's puppet is gone. Go finish it! Show us your loyalty, Morgana!

Morgana yells and left the arena. The wizards continue to fight Morgana's construct until it vanished for Morgana to arrive as they see her sobbing from her brothers death.

Douxie: Morgana.

Morgana: (Sobbing) It's your fault! You're the reason Arthur is gone!

Douxie: What?

Merlin: Gone?

Morgana angrily attacks them but Douxie uses his magic for shield.

Back in the battlefield, the gumm-gumms are winning as they're trying to take down the bridge while Galahad holds the dying king.

Arthur: Let the stories say Camelot fought to her dying breath.

With his last breath, the king has fallen in the battlefield.

Galahad: My king!

Gunmar: Their king is dead! Leave no survivors.

Earthbender: What are your orders, Toph?

Toph: To fight until the end!

YN: Brothers and sisters! We hold this ground in the name of our father. And if we die, we die vengeance on our lips!

The remaining earthbenders and knights round up to hold the line. Thankfully with YNs lava bending, he form a lava river defense to keep most of the gumm-gumms away as some tries to cross but fail by metling in the lava. They did everything they can to hold until everyone in the battlefield hear a war horn blowing as they see the trolls arrives to help. 

Callista: Hey, need some help? Because I brought some friends.

Toph: (Scoff.) Now they showed up.

Blinky: Yes! We are here to not run away!

Dictatious: Well said, brother!

Callista: Let's show these glorkheads how a real Troll fights!

The trolls all yells and charge into the battlefield as Callista holds the amulet.

Callista: For the glory of Merlin, daylight is mine to command!

With those words, she receive the Trollhunters armor and attacks the gumm-gumms before meeting up with Jim.

Jim: Callista, glad you made it!

Deya: It's Deya, actually. It always was.

Jim&Claire: Deya?

Bular fight off the humans until Steve comes back.

Steve: Hey, elephant neck!

Bular: Back for more? You fight like a lady.

Steve: Oh, I don't, but I have a friend who does.

The sea monster, aka Nimue arrives to face Bular.

Nimue: You are not worthy!

Before Bular could do any, the monsters tentactle slam him to the ground before grabbing and throwing him away.

Steve: Ha! That was for Lancelot! Thank you, scary fish lady.

Blinky and Dictatious fight off the goblins.

Blinky: Away, you vile jackanapes!

Dictatious: Be brave, brother! Stand valiantly against the tyranny of our oppressors.

Soon they were overwhelmed by more goblins as some of them keeps Blinky down and the rest take Dictatious.

Blinky: Dictatious!

Dictatious: Blinkous!

Blinky: Dictatious! Come back with him, you detestable swine!

Blinky tries to break free from the goblins until Aarg arrive and squashed the goblins like a bug.

Blinky: Aarg, you came back for me!

Aarg: Aarg like Blinky. Give hope. Paci-fist!

Blinky: That's not exactly how that works, but thank you, nonetheless. We must find my brother. This way, quickly!

Back with the magicians battle, Douxie still shields them from Morgana with Merlin's help.

Merlin: She's too powerful! We have no choice but to seal her away!

Douxie: I know. I'll try to buy some ti-

Morgana blast them with a powerful magic. Leaving Douxie face the witch alone.

Morgana: Oh, shame! Little Douxie finally gets his staff, just in time to die with it!

Douxie does his best to fight off Morgana alone.

Morgana: You can't even wield it! You should stick to your usual tricks.

Merlin: Use the power of your staff! Make it your own!

Douxie uses his staff to create something and unexpected created a electric guitar and swings it right to Morgana's face.

Knocking her against the wall.

Morgana: What!?

This amazed Douxie that he uses his staff to create an electric guitar.

Douxie: Bleeding balroths! This is nuclear!

Morgana: Did you just strike me with a- a lute?

Douxie: No, uh-uh. Spellcaster guitar, darling. Needs tuning, though.

Merlin: I meant make it your own weapon!

Douxie: Well, this is technically an "axe."

Douxie starts playing his guitar and evades Morgana's magic attacks.

Merlin: Hisirdoux, this is no time for dreadful music!

Douxie: Dreadful?

Morgana: Absolutely infernal.

Douxie: No worries, this is just the opening track!

Merlin: What do you hope to do? Blow out our eardrums!?

Douxie: Well, pardon me if this rock is too freakin' awesome for your medieval sensibilities!

Morgana: Enough of your noise!

They both clash their magic against each other, but Morgana's pushes her magic against Douxies.

Douxie: And nope. Plan B.

Douxie decided to use his guitar as a swinging weapon like an ax. But it was not enough as Morgana blast magical beam at him when he uses shield again.

Morgana: Do not fret, Merlin. You'll find a new apprentice to replace him. Are people not dispensable, after all?

Soon Archie arrives and blasted fire at her while tossing the staff to Merlin to break free.

Douxie: Archie!

Douxie gets an idea while Merlin foes his best to face Morgana.

Douxie: Arch, light me!

The wizard and his familiar combine their powers to release blue flames around Morgana to blind her surroundings until Douxie manage to freezes her in stasis for Merlin. 

Douxie: Hurry! I can't hold her that long!

Merlin: You've lost yourself, Morgana! Bound to dark magic.I have no choice but to seal you away! Sigilia infractum!

Merlin tries to seal Morgana away, but she manage to break free from the spell as Merlin collapse due to his injuries.

Douxie: Master.

Merlin: (Groans.) She's too powerful. You have to finish this alone.

Douxie: Sigilia infractum! Causera!

Douxie uses the same spell as Merlin uses and he successfully manage to seal Morgana.

Morgana: I will destroy you all! No matter what it takes, no matter where you go, I will end all that you love until you feel my agony!

Morgana blast magic at him but Claire protected him with her magic.

Claire: Hey! Hands off my teacher!

Morgana: I swear on your lives, I shall rise again!

Claire: Already seen it. You don't win. See you in 900 years!

Douxie successfully sealed Morgana before Claire teleported her away with her magic. Douxie collapse before Claire helps him up.

Claire: Douxie! Are you okay?

Archie happily licks his face as a dragon.

Douxie: Ugh! That's- That's disgusting! (Sighs.) Well I think we just saved history.

Archie: And took down a ninth-level sorceress. Merlin would be proud.

They see Merlin is sleeping while snoring due to the magic he used up.

Claire: Yeah, if he wasn't out cold.

Back in the battlefield, the remaining future teams fight off the gumm-gumms until Deya saves them.

Steve: She's awesome! Like some sort of super Troll fighter!

Jim: Yeah, but we need to get her to the bridge and past him.

They see Gunmar is between them and the killahead bridge.

Gunmar: Your king is gone! The only thing that rules now is fear.

YN: Oh no, I ain't doing this. Everyone get behind me! Earthbenders with me!

YN stands in front of his allies while the earthbenders join in as the gumm-gumms charge at them until YN signals them.

YN: Now!

The earthbenders uses their power to cause a massive earthquake that shakes the ground with their combined strength to disabled the gumm-gumms positions and to clear a path for the Trollhunter. Once Deya made her way to the bridge.

Bellroc: Mundane, simple creature. You stain magic. You are nothing in our eyes.

Deya swings her blade to Bellroc face. Screaming in agony before she was banished from killahead bridge. All that's left is to place the amulet on the bridge which Gunmar is in the way. But it didn't take long for them to fight until Deya place the amulet on the bridge and let it suck all the gumm-gumms into the Darklands as Gunmar faces Deya one last time.

Gunmar: Who are you that has brought the end of Trolls!?

Deya: Deya, the Trollhunter. And all I bring is the end of you!

She kicks Gunmar into the portal and sealed the killahead bridge for good. Ending the battle of the gumm-gumms for now.

Vendel: Thank you, Trollhunter. You delivered us.

Trolls: Hail, Deya the Deliverer!

Deya: (To Jim.) I couldn't have done this without you, Jim.

Jim: You're going to do great things, Deya. Oh, and when you're looking for a new Heartstone, skip New Jersey. Trust me, California has better weather.

Everyone recovered from the battle as some are taking the fallen including Lancelot.

Steve: Goodbye, Lancelot. I'll remember everything you taught me. I'll reform the Round Table, the knights will fight again, and they'll all have great hair.

Soon everyone sees the castle floating above them.

Galahad: Blessed be! Have you ever seen such a good sight?

Toph: I don't believe it. A castle leaving the people of Camelot? Its unacceptable.

YN: Camelot is gone the moment the king fell.

Toph: I know, we will round up the people and find a new place to call home.

YN: I'm afraid I cannot join. I am needed elsewhere. But best of luck.

Toph: I understand and you fight like a true earthbender. Mother Earth guides you.

YN: And to you, Toph.

The arcane order were force to fall back and hide.

Skrael: We miscalculated. The balance is lost.

Nari: (Sadden.) I feel so much pain. So many lives lost. This was not worth it.

Bellroc: We will readjust and return in time.

Blinky lost his brother in the battlefield while Aarg stands next to him.

Blinky: Oh, brother. Torn from this mortal coil! How will I carry on without you?

Aarg: Aarg alone, too. Aarg and Blinky be alone together?

Blinky: (Smiles.) I would enjoy a companion.

With that, its clear that the future team can now go back to the present as Douxie is setting up the time machine.

Douxie: Everybody, ready yourselves. We don't have much time. I'll dial us in for when we left.

YN: We can finally go back home.

Claire: But what's gonna happen when we get there? The danger we escaped, it'll be waiting for us. And Jim's still hurt.

Douxie: Claire, about that...Jim is-

Jim: Ready to face the inevitable.

Douxie: Jim, are you sure?

This confused Claire as she ask Jim.

Claire: Jim?

Jim: (Sighs.) Claire, the shard in...There is no cure. That's what Merlin told me earlier.

Claire: (Gasp.) That's crazy! We can find something! I'll learn a spell. We can stay here.

Jim: If we don't all go back right now,
the future won't exist. And what kind of hero would I be if I sacrificed everyone else? Not to be ironic, but we're out of time.

Claire: No! Douxie, tell him! We can fix this! You can fix this!

Douxie: I'm sorry, Claire.

Claire: YN?

YN: I'm sorry, Claire. Even if we did know if there's a cure. We won't have time to go back to our present. This is our only chance. Believe me when I say I don't take this lightly.

Douxie: He's right. We must go back now, but when we do, we'll find a way to reverse this. I promised I would return you home, and I am, but the portal can only stay open for a few moments. This is our one shot. Trust me.

Jim and Douxie shakes hands before Douxie opens the portal.

Douxie: You said to make the tough calls, old man. I hope I'm doing the right thing.

Soon a rift open for them and they uses the flying ship to get there since they couldn't take the castle with them.

Claire: There has to be another way. This isn't fair!

Jim: That seems to be a reoccurring thing with us. You sure you wanna keep dating me?

Claire: I'd date you for a hundred lifetimes, Jim Lake.

Jim: Hey, we'll figure this out. We always find a way to save each other.

Steve: Man, Camelot was crazy! Why don't they ever talk about that in the history books?

YN: Good thing we were there to see it.

When everybody boarded the ship, they fly towards the time rift.

Douxie: My burden to bear.

They finally jump through the rift to get back to the present. But the fight was far from being over.