A Mythril Blade is a Long Sword-class weapon Artifact available in Golden Sun: The Lost Age. It is only bought randomly by bringing a Mythril Silver forgeable material to the blacksmith in Yallam so that he may create one of several possible, randomly determined items from it, including this one.
The Mythril Blade increases the wielder's base Attack rating by 160 points. Its Unleash effect is Lethe Albion, with the standard base activation rate of 35%, which is a physical attack with an additional 56 points of damage added, and then the resulting damage is either increased or decreased based on how the user's Mercury power measures against the target's Mercury resistance. In addition, the effect may seal the target's Psynergy.
A Mythril Blade is a solid weapon for Piers to wield late in the game because its Mercury-based Unleash effect will be bolstered by Piers' naturally high Mercury power. It is often compared to the Levatine, the other weapon artifact that can be forged from a Mythril Silver, and the rarer-to-forge Levatine has higher power levels and has an Unleash that is of the Mars element and always ignores half of the target's Defense rating. Many players would identify the Levatine as a better weapon, but to be fair that would only be the unshakable truth if it's a Venus or Mars Adept who is considering equipping one of the two weapons. The Mythril Blade is a strong, solid weapon for the Mercury Adept warrior Piers to equip just as the Levatine is a solid weapon for the Mars Adept warrior Garet. If Piers is going to hold a water based weapon at the end of a linked game, the Masamune is probably superior to the Mythril Blade. The Masamune has a slightly higher base attack and bonus Mercury damage as well as a chance to do double damage.
A weapon to more validly compare a Mythril Blade to is the Rune Blade, which actually is practically identical to the Mythril Blade in every regard save for the fact the Rune Blade's Unleash effect is based on the Jupiter element instead of Mercury. However, while there is a Mercury Adept warrior like Piers to equip the Mythril Blade for enhanced damage, it is harder to optimize the Rune Blade's damage potential because there are no Jupiter Adept warriors that are able to equip Long Sword-class weapons.
As many other things in Golden Sun, the weapons' unleash (Lethe Albion) borrows from Greek Mythology. The river Lethe was a body of water in the otherworld that had the property of erasing the memory of any soul that drank from it. The in-game flavor is, of course, that the surge of water from the Lethe makes the foe forget its psynergy moves.
The other part, 'Albion', likely comes from latin Albus, meaning 'white' (also understandable in some respects as 'blank').
|Long Swords in Golden Sun|
|Long Sword • Broad Sword • Arctic Blade • Claymore • Great Sword • Shamshir • Silver Blade • Muramasa • Gaia Blade|
|Long Swords in Golden Sun: The Lost Age|
|Long Sword • Broad Sword • Storm Brand • Claymore • Great Sword • Storm Brand • Shamshir • Robber's Blade • Lightning Sword • Soul Brand • Cloud Brand • Hestia Blade • Huge Sword • Mythril Blade • Rune Blade • Levatine • Fire Brand • Darksword • Excalibur • Sol Blade|
|Long Swords in Golden Sun: Dark Dawn|
|Long Sword • Broad Sword • Storm Brand • Claymore • Great Sword • Shamshir • Sword of Dusk • Silver Blade • Muramasa • Rune Blade • Gaia Blade • Levatine • Fire Brand • Excalibur • Sol Blade • Darksword|