Mystery Blade

The Mystery Blade is a Light Blade found in Golden Sun. It is found on the second floor of Crossbone Isle. It can be bought for 6400 coins and sold for 4800 coins. Being a Light Blade, it can be equipped by Isaac, Felix, Garet, Jenna, Ivan, and Piers. It increases the wielder's attack by 84.

The Mystery Blade's Unleashed power is Life Nourish. Life Nourish converts all damage to Venus damage and attacks with an additional 25 damage points. Also, it has an excellent chance to heal the attacker by an amount equal to the damage dealt. Life Nourish appears as a swarm of purple motes of energy being pulled from the target to the attacker at the moment of contact.

While probably more powerful than anything found up to the earliest point Crossbone Isle can be accessed, Mystery Blade suffers because that point is right before arrival at Tolbi. In other words, the Assassin Blade, a stronger weapon with an instant-kill Unleashed power of the same element, is very likely to be gained shortly thereafter. While Life Nourish's Drain effect occurs far more frequently than Mortal Danger's Condemn effect, the higher attack bonuses of both the base weapon and Unleashed power are likely on their own to out-prioritize the Mystery Blade. However, if one acquires Hyper Boots at Tolbi, increasing the Unleash rate of the user's weapons, the more reliable effect of the Mystery Blade becomes a bit more desirable, making it possible that the weapon will remain in Isaac's possession for a fair portion of Gondowan.

It returns in Dark Dawn. It is obtainable in Harapa Ruins after defeating the Ice Queen. It has one new unleash: Spin Strike.