Muramasa

The Muramasa is a Long Sword-class Artifact weapon available throughout the Golden Sun series. It is a cursed item, which means that if an Adept equips it, he is inflicted with an equipment curse which causes him to be physically unable to de-equip it without assistance from a healer at a Sanctum. If he is not also equipped with the Cleric's Ring, then in battle there is a chance he may be immobilized, unable to do anything, whenever he attempts a battle command.

Basic Description by Game
In all appearances, the Muramasa increases the wielder's base Attack rating by 126 points. It can be sold for 10200 coins and subsequently rebought for 13600 coins.

In Golden Sun, it is found in a treasure chest in the ninth floor of the optional dungeon Crossbone Isle and is placed so that it is a prize for solving an optional puzzle. Being a Long Sword-class weapon, the Muramasa can be equipped on warrior-style Adepts, namely Isaac and Garet. The Muramasa's Unleash effect is Demon Fire. It has the standard base activation rate of 35%, which is a physical attack with an additional 60 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 inflict the Haunt status condition on the target. Visually, Demon Fire appears as a swarm of reddish spirit flames converging on the target while the attacker slides forward and strikes.

In Golden Sun: The Lost Age, the Muramasa can only be made available if it is transferred in a password-enchanced game. If transferred, both Felix and Piers can equip it. In a minor edit, The Muramasa's Unleash was changed to Demonfire.

In Golden Sun: Dark Dawn, the Muramasa is found in a treasure chest located in Harun Channel, and can be equipped by Matthew and Tyrell. The Muramasa retains Demonfire as an Unleash, but it is now a secondary Unleash, making the Muramasa one of the few weapons that doesn't have its former signature Unleash as its final learned Unleash. The Muramasa gains two additional Unleashes: Critical Move and Zenith Strike. Critical Move is a non-elemental physical attack that does 1.4 times the damage of a standard attack. Zenith Strike is a Jupiter-based Unleash that adds an additional 59 points of damage.

In Golden Sun and The Lost Age
In Golden Sun, the Muramasa is one of three cursed powerful weapons that can be found in Crossbone Isle, and its two counterparts are the Demon Axe and the Wicked Mace. When compared to each other, Muramasa has a Mars-based Unleash that may inflict Haunt, the Demon Axe has a Venus-based Unleash that may inflict Poison, and the Wicked Mace has a Venus-based Unleash that may inflict the more powerful Venom (and the fact it's a mace means more Adepts can equip it than the other two weapons). Since many players' endgame parties have Isaac equipped with the Gaia Blade and Garet safely equipped with a cursed weapon and the Cleric's Ring, consideration for which weapon Garet should finally be equipped with boils down to whether he should hold the Muramasa or the Wicked Mace (the Demon Axe is generally inferior to the other two). The Muramasa's Mars-based unleash gets increased damage with Garet's naturally high Mars level and particularly if he has all seven Mars Djinn Set onto him, but the Wicked Mace's unleash inflicting Venom is one of the most desirable side effects you can ask from an Unleash in this game because Venom will do large amounts of damage to enemies with high HP, like a Tempest Lizard. And giving Garet Venus Djinn so he is in the Berserker class makes the powerful Unleash attack even moreso, so it's possible the Muramasa is not as great on Garet as the Wicked Mace even though its Unleash is Mars-based. The only downside to using the Wicked Mace in this manner is that it sharply lowers Isaac's Venus power, leaving him unable to make full use of the Gaia Blade's potential.

If Muramasa is equipped on someone in your party when you complete Golden Sun and transfer the party into The Lost Age, then when the party joins Felix the weapon is merely "good", but already is outclassed by weapons such as the Mars-based Long Sword Hestia Blade, so it will very quickly be sold off.

In Dark Dawn
In Dark Dawn, the Muramasa's usefulness drops significantly. By the time it becomes available, the player will already have access to forged weapons that are much stronger. In addition, the Cleric's Ring is only available after the main portion of the game has been beaten, unless the player uses a glitch, and even then only close to the end of the game. Thus, they will have to deal with the side effects of using a cursed item. Taking both facts into consideration, the Muramasa may be ignored in favor of other, more useful, weapons.

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 sheathed.

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.