Heartslicers

The Heartslicers are the twin swords of the Hairy Scary Librarian. The Librarian was a skilled swordsman, and notorious for using these swords to kill anyone caught in the Meathead Public Library without permission. He attacked Hiccup Horrendous Haddock III, Camicazi, and Fishlegs when he discovered them in the library, and was able to duel Hiccup and Camicazi simultaneously (though he was put out at his inability to finish them quickly).

Madguts the Murderous confiscated the Librarian's swords when he took the Librarian as a slave to the Ugli Lowlands.