Shamshir

A Shamshir (Gran Shamshir in the Japanese version) is a Long Sword-class Artifact weapon found throughout the Golden Sun series.

Basic Description by Game
In all its appearances, the Shamshir increases the wielder's base Attack rating by 99 points. It can be bought for 10000 coins and sold for 7500 coins. In Golden Sun, it is sold as an artifact at the weapon vendor in Lunpa that opens after completing the Lunpa Fortress optional event, and can be equipped by Isaac and Garet. In Golden Sun: The Lost Age, it is sold as an artifact in the general vendor in Izumo which is accessible as soon as you gain the Lemurian Ship and start exploring the Great Eastern Sea. The Shamshir can be equipped by Felix and Piers. Its Unleash effect is Acid Bath, with the standard base activation rate of 35%, which is a physical attack with an additional 34 points of damage added, and then the resulting damage is either increased or decreased based on how the user's Mars power measures against the target's Mars resistance. The Unleash may also decrease the target's total Attack rating by 25% (the maximum amount any character or enemy in the game can have its Attack rating increased or decreased by is up to 50%, so this side effect can successfully occur twice profitably). Visually, Acid Bath resembles a physical attack with a purplish vapor-like cloud released on impact.

In Golden Sun: Dark Dawn, the Shamshir is sold as an artifact in the town of Tonfon, and can be equipped by Matthew and Tyrell. It retains Acid Bath as its signature unleash, and gains two secondary Unleashes: Power Charge and Fearless Attack. Power Charge is a Mars-based unleash with a damage multiplier of 1.4. In addition, Power Charge has a chance of decreasing the target's Defense by 25% when attacking. Fearless Attack is a non-elemental Unleash with a damage multiplier of 1.7.

Analysis
In Golden Sun, the Shamshir is essentially a buyable "reward"  artifact for completing the optional Lunpa  Fortress dungeon and its  boss Toadonpa, and it is sold alongside a  similar weapon artifact  named the Dragon Axe. Both are strong weapons and should be bought for your two warrior Adepts. Note that both weapons' Unleash effects are Mars-based so they will do more damage for  Garet than Isaac, but exchanging Venus and Mars Djinn between them so  that they're both in the  Brute class series is very sound for  increasing damage and power in  general. The Shamshir generally remains in the party unil arriving at  Lalivero.

In Golden Sun: The Lost Age, the Shamshir is effectively one of the many weapon artifacts that become instantly available once the party opens up the Great Eastern Sea for exploring with their newly acquired Lemurian Ship, and while it's probably not a bad weapon to buy, the fact your Mars Adept Jenna can not equip it as a Long Sword hurts its overall usefulness to your party because its Unleash effect is Mars-based. It is conceivably useful if you specifically keep Felix in the Mars Djinn-based Savage class to increase both his natural battling ability and his Mars power level, however.

In Dark Dawn, the Shamshir is not available until the player gains access to the ship. By this time, Matthew and Tyrell will both have weapons that outclass the Shamishir. In addition, the player will have access to many forged weapons that are significantly stronger than the Shamshir. Thus, it is suggested that the player avoid the Shamshir in favor of these stronger weapons.