When the Lich is accidentally freed from its amber prison in Princess Bubblegum's Castle, Finn and Jake must head forth to stop it from regaining its full power, all while being pestered by the Ice King to give him their blessing to marry Princess Bubblegum.
In Part One, Finn, Jake, and Princess Bubblegum are meditating on the balcony of the castle. At first the boys have trouble concentrating, but the princess tells them to clear their minds and it works. Finn has a vision of himself older and cooler with new powers such as having a mechanical arm. Jake has a vision of Lady Rainicorn riding a horse. Princess Bubblegum has a vision of a dark figure and panics before saying she needs to check on something and Finn and Jake decide to go with her. She gives Finn and Jake gems like the one in her tiara before entering a secret room in the heart of the tallest tree where she shows them an ancient evil sorcerer called The Lich (or The Lich King) held in a prison of amber and explains that the gems will keep themselves safe from the Lich's spells that control and possess people.
Then she tells the story of how he plotted to destroy Ooo and kill everyone until The Hero Billy pushed him into the resin of the amber. As she explains, however, the waving Snail climbs out of Finn's backpack and is quickly possessed by the Lich, as it is not wearing the jewelry. The Snail makes a crack in the amber, and the Lich is quickly freed. When Finn and Jake try to stop him, the Lich escapes and heads towards the skies. Princess Bubblegum then takes them to the other secret room and gives Finn The Gauntlet of the Hero Billy, a gauntlet that Billy used to defeat the Lich the first time, and tells him to smite the Lich with it before he gets to his Well of Power and gets his magic back. She also tells Finn that the Lich's lair is cold so she gives him a sweater that she made, telling him she cares for him. As one last parting the trio hugs each other for good luck.
While they're hugging, a latched window opens up revealing the Ice King who butts in, asking Finn and Jake to bless his wedding with Princess Bubblegum, which of course they refuse to do. As they journey to find the Lich, the Ice King repeatedly begs for the blessing. After Finn uses the gauntlet on him, the Ice King gives up on the blessing and kidnaps the princess while she is eating ice cream in hopes that Finn and Jake are alright. All the while, Finn and Jake are in pursuit of the Lich, following the destruction he has left behind. As they reach the end of Iceberg Lake, just as Finn prepares to smite the Lich with the gauntlet, the Ice King interrupts them yet again to show them he kidnapped Princess Bubblegum. While he does this, the Lich makes it to his well releasing hundreds of evil souls from the entry, so Finn and Jake hurry down, and the Ice King follows.
Finn manages to fight off the Skeletal Guards that try to block his path, but his pack is ripped to bits while fighting. After blowing a hole in the ground with the gauntlet, Finn manages to grab hold of a hanging pipe leaking toxic waste, which forms the Lich's Well of Power in the chamber below, where The Lich begins his power rejuvenation. Finn tries to smite the undead creature with his gauntlet, but the Lich, having regained some of his old power, grabs hold of Finn's wrist and turns the gauntlet to dust, burning Finn's hand in the process. With their main weapon destroyed, Jake tries to 'bark' the villain, but is struck in the face with fire and knocked out, and when he falls, Finn's protective jewelry breaks and the Lich successfully possesses Finn's body in an instant.
The Lich compels Finn to walk into his Well of Power, asking him if he is cold, but Finn resists his influence by screaming, "I HAVE A SWEATER ON!!!" The Lich, having failed to take control of Finn's body completely, decides to destroy him with his flames, but they too fail to kill him. Finn realizes then that the sweater Princess Bubblegum made for him is keeping him safe, for it has the power of love in it, but Finn feels embarrassed saying love so he says "Liking someone a lot."
Finn fully escapes the Lich's possession, and charges at him with his sweater, jumps on him and pulls the sweater through his eye sockets. As the Lich struggles, trying to burn Finn while laughing hysterically, Finn pulls the sweater vigorously upwards until the Lich's face is broken off and his body turns to dust. After Jake makes sure Finn is okay, the Ice King, in celebrating the victory he had no part in, decides to set Princess Bubblegum free, but in doing so, he stupidly drops her into the boiling well, much to Finn and Jake's horror.
- Peppermint Butler
- Skeletal Guards
- Boyfriend & Girlfriend Skeletons
- Lady Rainicorn (in Jake's thoughts)
- "Mortal Folly" can mean "a foolish death" or "a fatal and foolish act." This could be referencing how Ice King almost foolishly killed Princess Bubblegum.
- This and "Mortal Recoil" make the first two part episodes in the series.
- Ice King was in the presence of the Lich without the protection of Princess Bubblegum's gems. It is implied that he was able to do this because of his crown.
- The Lich's lair is in a subway station from before the Mushroom War.
- Outside the Lich's lair on a pole is the number 81012.
- The same numbers can also be seen on the right wall as Finn and Jake fall down through the hole, just before Finn grabs the leaking pipe, and right afterwards on the wall directly behind the two.
- One of the Lich's horns is broken, but it is not broken in Princess Bubblegum's vision.
- The depiction of himself Finn imagines while meditating appears again as Finn's 28 year old future body in the Adventure Time Comic Issues 2, 7, 8, and 9.
- Finn can move the six fingers in the gauntlet, but he only has four fingers. The gauntlet and its usage in the episode may be a reference to Michael Moorcock's character Corum Jhaelen Irsei, who at one point possessed an artifact Hand of Kwll. Much like its Adventure Time counterpart, the Hand looked like a jeweled right-hand six-finger gauntlet that could at times act of its own accord, and it was given to Corum to help him avenge his kin and vanquish the Chaos Gods.
- If you look closely at one of the wrecked subways, one appears to have two jet engines mounted on top of it.
- This episode and "The Enchiridion!" are featured in the Lego Dimension Adventure Time Level Pack.
- The plot of this episode is continued in "Mortal Recoil."
- Iceberg Lake from "Business Time" returns as Finn and Jake pursue The Lich, also confirming it as the location of the Gauntlet dock, which still hangs over the lake.
- When Billy is shown using his gauntlet in "His Hero," he wears it on his left hand, but it is a right-handed gauntlet in this episode.
- When Finn meditates, he imagines himself older, stronger and has a robotic arm similar to Farmworld Finn in "Finn the Human (episode)." Finn does eventually get a prosthetic arm in "Two Swords."
- When Finn pulls back his hat, one can see his blonde hair that has been growing back since "To Cut a Woman's Hair."
- The title art looks identical to the explosion let off from the bomb in "Jake The Dog."
- The well in the Lich's lair looks like the same mutagenic material that turned Farmworld Jake into the Lich in "Jake the Dog."
- The Lich's well is shown again in "Whispers."
- When Princess Bubblegum moves to the chest containing the sweater she wants Finn to have, the earring is not present on Finn's head. It returns when she brings the sweater over to Finn.
- When Finn and Jake are confronting Ice King after he creates an Ice Dome around them, the heart stitches on Finn's sweater disappear.
- When the Ice King first appears in this episode, he says "Hey hey hey!" the same way as said in the 1980s sitcom What's Happening!!
- This episode was previously titled "This Mortal Folly" and is listed as such in AT&T U-Verses' description of the episode as well as on iTunes.
- This episode and "Mortal Recoil" would have been the final episodes of the season prior to the rescheduling of "Heat Signature." The two-part episode is still considered the season two finale by the show's crew and appears as such on the Complete Second Season DVD and Blu-Ray.
- The Lich would not have been released if Princess Bubblegum had not taken Finn and Jake to check on the Lich's prison, due to the fact that the snail got there via Finn's backpack; her vision was itself a self-fulfilling prophecy.
This episode was censored in some countries. See Censorship of Adventure Time for more information.
- ↑ Pen Ward refers to "Mortal Folly/Mortal Recoil" as season finale, even after the scheduling change. http://twitter.com/#!/buenothebear/status/65160425511202816