Storm Brand

The Storm Brand (ストームブレード, Sutōmu burēdo^?, lit. Storm Blade) is a Long Sword-class Artifact weapon found in Golden Sun: The Lost Age and Golden Sun: Dark Dawn.

In Golden Sun: The Lost Age

Storm Brand (TLA)
Visual effect of Hurricane
In-Game Description
"Long Sword: Unleashes Hurricane" (TLA)
Trade Info
Weapon class	Long Sword
Buy value	3900
Sell value	2925
Artifact?	Yes
Statistic Boosts
Attack Boost	60
Unleash effect
Effect name	Hurricane
Extra damage	21
Side effect	May lower the target's Attack by 25%
Acquisition
• Chest at Air's Rock (TLA)

In The Lost Age, any time during your stay in Osenia early in the game, you can play through the entirety of the dungeon Air's Rock in Osenia's center desert. The first screen of the location is a large and complicated maze where you must cast Whirlwind on the "Wind Stones" to clear away walls of sand blocking your progress. The chest containing the Storm Brand is enclosed within the northeast corner of the sand maze, and you will have to approach there from the ground level first so that you can clear the wall blocking the path to it in advance. Then, you will have to use a separate ladder to climb up to the cliff screen above the sand maze, then climb down another ladder at the far lower-right corner of that screen to make it back down to the chest's enclosed corner.

The Storm Brand's Unleash effect is Hurricane (バッドハリケーン, Baddo harikēn^?, lit. Bad Hurricane), which adds 21 points of flat damage, aligns the overall attack to Mercury, and carries a 60% base chance to reduce the target's Attack stat by two 12.5% "stages" for several turns (down to a maximum of four stages totaling -50%). Hurricane appears as a very narrow, slightly slanted torrent of line-like rain drops dropping onto the target before the wielder leaps forward to deal a physical strike.

Air's Rock is generally played through after the player completes Yampi Desert and makes a stop at Alhafra on the other side. Along the way, the Blow Mace weapon artifact can be found in a chest, decisively outperforming any other weapon available to the party by that point, and the Storm Brand continues the trend of being clearly more powerful than that. If the Blow Mace is equipped to Felix, the Storm Brand can be equipped onto him in its place, allowing the Blow Mace to be handed down to Sheba. It becomes the best weapon available for battling Briggs and his Sea Fighters at Alhafra if you do not battle them as soon as you are able (though its chance to lower Attack is only really applicable to the Sea Fighters).

The Storm Brand will remain on Felix until you find the Disk Axe in Kibombo Mountains. In the likely event you keep the Storm Brand in your inventory, you can equip it to Piers as soon as he is added to your party in Kibombo, which will amount to a slight Attack upgrade over the generic Battle Mace he is equipped with at first. The Battle Mace will not have an Unleash of its own, whereas the Storm Brand will provide Piers an Unleash that is significantly enhanced by his naturally high Mercury Power, making that a noticeably superior weapon for him overall. (Don't forget that each Elemental Level Piers has in the Mercury element will give him an additional 1% probability of applying the Attack drop when Hurricane hits.)

The Storm Brand will remain Piers' best weapon (unless you buy him a 70-Attack Claymore at Kibombo) up through the Aqua Hydra boss battle, but the party will gain much stronger weapon artifacts quite quickly as you begin progressing through the Eastern Sea arc of the game. (For example, you can reforge the Captain's Axe at the blacksmith in Yallam for its 95 Attack, and the 110-Attack Mist Sabre is a treasure in one of the earliest dungeons available in the Eastern Sea, Aqua Rock.)

The Storm Brand, incidentally, is an almost-identical clone of the Arctic Blade from the first game, save for having 5 more Attack and adding 3 more damage than the Arctic Blade's Blizzard Unleash effect. Like the Arctic Blade in Golden Sun, the Storm Brand is the first available Unleash in The Lost Age that potentially lowers attack.

In Golden Sun: Dark Dawn

Storm Brand (DD)
The DS model of the Storm Brand
In-Game Description
"Weapon: Long Sword" (DD)
Trade Info
Weapon class	Long Sword
Buy value	3900
Sell value	2925
Artifact?	Yes
Statistic Boosts
Attack Boost	60
First Unleash effect
Effect name	Critical Strike
Extra damage	x1.5
Second Unleash effect
Effect name	Hurricane
Extra damage	21
Side effect	May reduce target's Attack 25%
Acquisition
• Chest in Barai Temple (DD)

In Dark Dawn, the Storm Brand is found in a treasure chest in Barai Temple and is similarly impactful as the best weapon either Matthew or Tyrell could be wielding at that point. It will be the first weapon the player comes across that can reduce the target's Attack stat, but like with all other weapons in Dark Dawn, it now only has a chance to pick Hurricane whenever it Unleashes. Its other possible Unleash is the extremely generic Critical Strike (かいしんのいちげき, Kaishin no Ichigeki^?, lit. Critical Hit), which deals 50% increased damage without aligning the attack to an element.

Giving Mercury Djinn to either Matthew or Tyrell will put them in their versions of the Swordsman class series (which, in Matthew's case, now starts off with the first class stage being called Crusader). It features the same Attack scaling as Matthew's innate Squire class series (which is better than that of Tyrell's innate Guard class series), and the Set Mercury Djinn will provide an additional dose of Mercury Power to improve the damage of the Storm Brand's Hurricane on the occasions where that Unleashes.

The next easily acquired weapon artifact for either Matthew or Tyrell is the Vulcan Axe in the Ouroboros, which has an impressive 16 additional Attack and automatically aligns all its physical strikes with Mars if they don't have elemental alignments already. It can be given either to Matthew for higher damage with a given blow or to Tyrell because of his high Mars Power, especially while he remains in his mono-elemental Guard class series. In either case, the other warrior Adept will still be using the Storm Brand until Harapa Ruins at the earliest, where the 84-Attack Mystery Blade can be found. Then, the party can find the 88-attack Grievous Mace in Craggy Peak Ruins.

Gallery of Dark Dawn unleashes

• 

  Critical Strike

• 

  Hurricane