Furnace is the nephew of Flame King and the cousin of Flame Princess.


His father was killed by his uncle in order to take the throne. As a result of this, Furnace and his brother Torcho attempted to assassinate their uncle by pouring ice over him as he watched a play, but were foiled by Finn and Jake who overheard them discussing their target and decided to intervene on their assassination.

Furnace speaks with a hiss inflection in his voice. Finn and Jake use this recognisable trait to track him down since they had yet to see his appearence after hearing him talk about his plot to Torcho, and this leads them to accidentally mistake Jalapeño pepper for him when a snake on Finn's shoulder hisses as Jalapeño pepper speaks. Eventually Furnace's hissing enables Finn to recognise him as the conspirator when he is disguised as an executioner. After Torcho and Furnace's plot is exposed, they are both put in a "Punishment Room."


  • Like everyone else in the Fire Kingdom, according to Flame King, Furnace is evil.
  • Finn and Jake identified him by his hissing sound.


           Adventure Time Villains

The Lich | Ice King | Marceline Abadeer | Lumpy Space Princess | Gunter | Hunson Abadeer | Earl of Lemongrab | Flame Princess | Martin Mertens | Uncle Gumbald, Cousin Chicle and Aunt Lolly | Fern | Ricardio | Death | Marshall Lee | Ice Queen | Patience St Pim | Dr. Gross | Shoko | Magic Man | Betty Grof | AMO | Vampire King | The Fool | The Empress | The Hierophant | The Moon | Ash | Flame King | Fire Count | Don Jon | Fire Kingdom | The Guardian | Gareth | Flying Lettuce Brothers | Tiffany Oiler | Guardians of Sunshine | Ooze Monsters | Fear Feaster | Kee-Oth | Maja the Sky Witch | Darren the Ancient Sleeper | Goliad | Blargetha | Demon Cat | Guardian Angel | Wendy, Booboo & Georgy | Stag | Scorcher | Jaybird | Smudge | Princess Cookie | Tree Witch | Xergiok | Me-Mow | Alpha Hug Wolf | Evil Monster | Donny | The Glitch | Grassy Wizard | Fight King | Furnace | Torcho | Gnome Ruler | Sir Slicer | King Worm | Blanket Dragon | Little Dude | Cute King | Why-Wolves | The Hooligans Who Love Candles