Cloud Brand

The Cloud Brand is a Long Sword-class weapon Artifact available in Golden Sun: The Lost Age, and is one of the few pieces of equipment that actually has a bearing on the overall story of the game. It is found after beating the Serpent boss battle in Gaia Rock, hidden at the end of a stream of fluid that replaces the tail of the dead beast in a sandy area behind rocks, and it can only be reached by using the Sand Psynergy you gain after the battle. Being a Long Sword-class weapon, the Cloud Brand can be equipped on warrior-style Adepts, namely Felix and Piers, and also Isaac and Garet when they join up late in The Lost Age. Its buy value is 11800 coins and its sell value is 8850 coins.

As a piece of equipment, the Cloud Brand is a strong weapon that increases the wielder's base Attack rating by 130 points. Its Unleash effect is Raiden's Wrath, which is one of the few Unleashes that activates at a rate of more than 35% of the time (40%, specifically), and it is a physical attack with an additional 39 points of damage added, and then the resulting damage is either increased or decreased based on how the user's Jupiter power measures against the target's Jupiter resistance. The Unleash also always treats the target's Defense rating as zero each time it activates, making the Unleash a good deal more powerful than any other Unleash at that point in the game. (The Cloud Brand is the only weapon in the entire game that can ignore the target's defense completely, and it does so with 100% success rate, making it especially noteworthy.) Visually, Raiden's Wrath resembles the appearance of a green humanoid monster (Oni)with white hair and holding a sword laced with electricity, who is most likely what the name "Raiden" refers to, and Raiden appears extremely briefly as he slashes the target once while the wielding Adept performs a normal attack. Raiden, or Raijin, is the Japanese god of thunder.

The Cloud Brand is one of the best weapons you can get in the Great Eastern Sea because of its Unleash effect, in spite of the fact that on its own the Cloud Brand's attack rating is lower than the Hestia Blades you can get in Lemuria and the fact it's Unleash is based on the Jupiter element, and no Jupiter Adept can equip a long sword to capitalize on this elemental affinity. Felix and Piers are the first Adepts that can equip the weapon, and it will definitely be powerful as a weapon nonetheless in their hands. The strong damage of its Unleash effect can be even higher if the wielding Adept is wearing Aerial Gloves, an item that can be forged from a Sylph Feather and increases Jupiter power. It is a good weapon to use against several boss encounters in The Lost Age, including the Avimander (if fought after the Serpent), Poseidon, and Moapa. While it will eventually be outpowered by weapons such as the Phaeton's Blade by the time Isaac's party eventually joins, if Isaac's party is only wearing generic equipment because the game is being played either without data transfer or a low-level Password data transfer, the Cloud Brand is a sound weapon to equip on either Isaac or Garet for the time being until stronger weapons can be amassed.

Story
In the story of The Lost Age, people in the town Izumo describe the Cloud Brand as a "dagger" even though it is a big long sword, and it originally belonged to one of the old men living at Izumo. It is the subject of the following piece of folklore: Long ago, the Great Serpent of Mikage would sleep with its body crossing the river. Where its tail fell, the Cloud Brand lay hidden. The Serpent was once the protector of the sword, but it "lost the sword" many ages past. When said Serpent awakens in Gaia Rock (a.k.a. Mount Mikage) and begins terrorizing the town, Izumo warrior Susa takes the Cloud Brand, goes into Gaia Rock, and spends a lot of time weakening the beast with barrels of a deluding fluid called Dragonsbane (Sake in the Japanese version).

By the time Felix's party explores the dungeon and arrives at the chamber, Susa attempts to stab the Serpent with the Cloud Brand, but the monster is too strong and retaliates, and Felix's party engages in an intense battle and eventually defeat the Serpent. Susa finishes the job with another stab of the Cloud Brand, turning the monster into stone and evaporating its tail into a thick fluid. He secretly hides the Cloud Brand at the end of the fluid trail (the area where the tip of the Serpent's tail used to be, in a nod to the old folklore) right afterwards before thanking Felix and leaving. If Felix's party does not retrieve the sword for themselves right then, they can come back for it later after Susa in Izumo relates the sword's folklore and hints to them that he left the Cloud Brand back at the scene for them to take for themselves as a thanking reward.

Cultural Reference
Raiden, literally meaning "Thunder and Lightning" in Japanese, was the god of his namesake. He was said to eat the abdomens of children and was often depicted with Fujin, the God of Wind.

The sword itself may also be a reference to the Kusanagi no Tsurugi, the sword that was found in the tail of the serpent Orochi, given how the names of Susa and Kushinada are taken from characters from the same story.