Demon Blood Sword

The Demon Sword is the sword that Joshua formerly owned. It is the family sword, and is the prize at the end of Joshua's Dungeon, which Finn and Jake were sent to explore in the episode "Dad's Dungeon." It is made entirely out of Demon blood, as explained by Joshua in the hologram video that he made for Finn and Jake in the future. The sword has a Celtic cross on the hilt. It was found in the last chamber of the dungeon, where Finn uses it to defeat the Evil Monster. It was locked up with chains and stuck in a formation of crystals when Finn found it; the key for it was around a monster's wrist. Instead of defeating the monster to get the sword, Finn ripped it from the crystals, breaking the chains, and subsequently used the sword to defeat the monster.

This sword replaced the Root Sword that Finn found in "Mystery Train." Finn uses this sword for the first time (not counting "Dad's Dungeon") in the episode, "Return to the Nightosphere." It seems that the design for the sword was slightly changed for that episode; the tip of the handle is white instead of red.

Trivia

 * This is the level 7 sword on Finn and Jake's Epic Quest.
 * It seems like that the appearance of the Demon Sword is changed since the episode "Return To The Nightosphere" (the tip of the handle is white instead of red like in "Dad's Dungeon," and it keeps being white after that episode).