Muramasa

The Muramasa is a Long Sword found in Golden Sun. It is located on the ninth floor of Crossbone Isle, and so cannot be gained until the party gains the Carry Stone and can bypass the seventh floor. Being a long sword, it can be equipped by Isaac, Felix, Garet, and Piers.

The Muramasa increases the wielder's attack by 126. Its Unleashed power is Demon Fire, which adds another 60 attack points, converts the damage from physical to Mars, and attempts to inflict haunt on the target. It has the standard base unleashing rate of 35%. Demon Fire appears as a swarm of reddish spirit fires converging on the target while the attacker slides forward and strikes. The Muramasa is also cursed, meaning that if the wielder isn't also wielding the Cleric's Ring, there is a chance that he might not be able to act in a given turn, and must go to a sanctum and pay a healer to unequip it. It can be bought for 13600 coins and sold for 10200 coins.

If one elects to give him the Cleric's Ring, the Muramasa is a very good fit for Garet--being fire-aligned, it will always have a notable bonus from his Mars power level. If he has any Venus Djinn equipped, though, the Wicked Mace (inflicts venom) and Demon Axe (base attack bonus of 132) might be a better idea.

Cultural references
Muramasa Sengo was a famous swordsmith in Japan during the 16th century, with his blades renowned for their sharpness. However, he was also regarded as being violent and somewhat insane. Since swords were supposed to inherit a measure of their smith's psyche, Muramasa's blades were thought to share his bellicosity, thirsting for blood. Tokugawa Ieyasu apparently thought Muramasa's blades were out to get his family (several of his relatives and retainers had been killed and/or wounded by Muramasa blades, and he had been badly cut by a Muramasa wakizashi and yari himself), and so ordered their confiscation (one wonders whether rumors of Muramasa's psychosis began before or after this). In popular Japanese culture, Muramasa's blades are often depicted as outright cursed, usually needing to be sated with (fatally) drawing someone's blood before they'll let themselves be unsheathed.

A legend about the blades of Muramasa and Masamune says that to compare the workmanship of the two, one blade created by each swordsmith was placed in a stream with free-floating leaves. Leaves, fish, etc. that touched the Muramasa blade were cut cleanly in two, whereas anything that approached the Masamune blade changed course to evade it, a testament to Masamune's calm soul which refused to kill or destroy anything that did not need to be.