Durandal

Durandal is a sword. It is especially effective when fighting daemons.

Source
Durandal can be purchased from Culless Munitions at Meldacio Hunter HQ (anytime) and Hammerhead (Chapter 14) for 10,000 gil. It can also be found as a collectable in the Costlemark Tower dungeon. It can be sold back to shops for 5,000 gil.

Trivia

 * Durandal refers to the sword given to the military leader (or paladin) Roland by King Charlemagne in the French epic poem The Song of Roland. It was claimed to be the sharpest sword in existence, capable of cutting stones with a single swipe, and it was indestructible.