Mythril Blade

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. Being a Long Sword-class weapon, the Mythril Blade can be equipped on warrior-style Adepts, namely Felix, Piers, Isaac, and Garet. Its buy value is 14600 coins and its sell value is 10950.

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. Visually, Lethe Albion is an elaborate effect resembling the user summoning a rushing river that flows through and damages the target as it is engulfed in a giant holographic blue image of a Psynergy Seal.

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.

Cultural References
As many other things in Golden Sun, the weapons' unleash (Lethe Albion) borrows from Greek Myth. The river Lethe was a body of water in the otherworld that had the property of erasing the memory of any sould that drank from it. The in-game flavor is, of course, that the surge of water from the Lethe makes the foe forget it's psynergy moves.

The other part, 'Albion', likely comes from latin Albus, meaning 'white' (also understandable in some respects as 'blank').