Dyrnwyn

Dyrnwyn was a magical sword and the most powerful weapon in Prydain. For some time it was only thought to be legend until found by Princess Eilonwy and Taran during their escape from Spiral Castle. It was located in the depths of the castle with the body of King Rhitta, the last person to bear the sword before its rediscovery. The blade's removal caused the castle to collapse.

Dyrnwyn was sheathed in a black scabbard with an ancient inscription, though much of the writing had been scarred and obscured by Rhitta in his last madness. When made clear by magical means, such as Eilonwy's bauble, the inscription read "Draw Dyrnwyn, only those of noble worth (sometimes mistranslated royal blood), to rule with justice, to strike down evil. Who wields it in good cause shall slay even the lord of death."

The blade's enchantment made it deadly to even the deathless Cauldron-Born. However, it could be willful to those it deemed unworthy of its power or not yet ready for it, either refusing to be drawn or burning the wielder.

Eilonwy bore the weapon, undrawn, from its finding until the confrontation with the Horned King at Caer Dathyl, at which point Taran attempted to draw the blade. The Assistant Pig-Keeper was scorched but the evil war leader was distracted at a crucial moment, allowing his destruction by Gwydion. Gwydion then bore the blade until the events of The High King, when Arawn stole Dyrnwyn through deception and an ambush. It was later rediscovered by Taran and wielded by him against the dark lord.

In the spongebob series, Dyrnwyn appears, playing the same role it had in the original Black Cauldron movie. Only now, it has a larger role to play. As it turns out, the sword, Benny's Excalibur blade, Leo's Sword of Righteousness, and the Kingdom Keys of Light and D are needed in order to create the Xblade, the very weapon which the High Council used to defeat Chernabog in the First Cartoonian War, and is now being used in irony by the dark lord himself. Actually, the Xblade that Chernabog uses right now is actually a disfiguired copy created by the darkness. Currently, Dyrnwyn is.