Mystery Blade

The Mystery Blade (ミステリィソード, Mystery Sword^?) is a Light Blade-class Artifact found in Golden Sun and Golden Sun: Dark Dawn.

In Golden Sun

Mystery Blade (GBA)
Visual effect of Life Nourish
In-Game Description
"Light Blade: Unleashes Life Nourish" (GS) (TLA)
Trade Info
Weapon class	Light Blade
Buy value	6400
Sell value	4800
Artifact?	Yes
Statistic Boosts
Attack Boost	84
Unleash effect
Effect name	Life Nourish
Extra damage	25
Side effect	May heal the user by the amount of damage inflicted.
Acquisition
• Chest in Crossbone Isle (GS)

In Golden Sun, the Mystery Blade is found on the second floor of Crossbone Isle, and can be equipped by Isaac, Garet, and Ivan. The Mystery Blade's Unleashed power is Life Nourish (ライフナリッシュ, 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.

In Golden Sun: Dark Dawn

Mystery Blade (DD)
The DS model of the Mystery Blade
In-Game Description
"Weapon: Light Blade" (DD)
Trade Info
Weapon class	Light Blade
Buy value	6400
Sell value	4800
Artifact?	Yes
Statistic Boosts
Attack Boost	84
First Unleash effect
Effect name	Spin Strike
Extra damage	0
Side effect	Hits each adjacent foe
Second Unleash effect
Effect name	Life Nourish
Extra damage	25
Side effect	May heal the user by the amount of damage inflicted.
Acquisition
• Chest in Harapa Ruins (DD)

In Dark Dawn, the Mystery Blade can be found in a chest on the third basement level in the Harapa Ruins, but is only accessible after the player has defeated the Ice Queen. Besides its signature Life Nourish unleash, it gains the Spin Strike (かいてんぎり, Spin Slash^?) unleash. Spin Strike converts all damage to Jupiter damage, and is one of a few unleashes to have a range of 3 targets. As a Light Blade, it can be equipped by Matthew, Tyrell, Karis, Amiti, Eoleo, and Himi.

In Dark Dawn, the Mystery Blade will outpower any other weapon available to that point. The Venus-based Life Nourish unleash makes it a good weapon for Matthew, while the Jupiter-based nature of Spin Strike means that Karis could make use of the Mystery Blade as well. It is worth noting that the Grievous Mace, a Venus-based pure element weapon, will be available in the next major dungeon, and would most likely make a better choice for Matthew.

Gallery of Dark Dawn unleashes

• 

  Spin Strike

• 

  Life Nourish