Storm Brand

The Storm Brand is a Long Sword-class Artifact weapon available in Golden Sun: The Lost Age and Golden Sun: Dark Dawn.

Basic Description by Game
In all appearances, the Storm Brand increases the wielder's base Attack rating by 60 points. It can be sold for 2925 coins and subsequently rebought for 3900 coins.

In The Lost Age, it is found in a treasure chest in the first screen at the bottom of the massive Air's Rock dungeon, and can be equipped by Felix and Piers. Isaac and Garet can also equip the Storm Brand, but the weapon will be outclassed by the time they join the party. The Storm Brand's Unleash effect is Hurricane, with the standard base activation rate of 35%, which is a physical attack with an additional 21 points of damage added, and then the resulting damage is either increased or decreased based on how the user's Mercury power measures against the target's Mercury resistance. The Unleash may also decrease the target's total Attack rating by 25% (the maximum amount any character or enemy in the game can have its Attack rating decreased or increased is up to 50% from the norm, so this side effect can successfully occur twice profitably). Visually, Hurricane resembles a torrent of rain drops hitting the target before the holder of the sword attacks them physically.

In Dark Dawn, it is found in a treasure chest in Barai Temple, and can be equipped by Matthew, and Tyrell. The Storm Brand retains Hurricane as its signature Unleash, but also gains a secondary Unleash, Critical Strike. Critical Strike is a non-elemental physical attack that deals 50% more damage than a standard physical attack.

Analysis
The Storm Brand is a textbook example of a weapon artifact in The  Lost Age that is found in a chest in one of  the  game's big  dungeon-style locations, and when it can first be found it is noticeably strong, certainly stronger than any weapon Artifact that you can buy from vendors at the time. It is easily the strongest weapon you can find yet for Felix during your first visit to Osenia   and is useful to  use in the Briggs boss battle, in spite of the fact Felix is a Venus Adept and the weapon's Unleash effect is Mercury-based.

When travelling into lower Gondowan sometime  afterwards, the Storm Brand will be outclassed by the Disk Axe you  can find in Kibombo Mountains,  but it is advisable to keep it in  your inventory for when the Mercury  Adept warrior Piers joins your  party shortly afterward. He will be holding a Battle Mace, but the  Storm Brand is an instant perfect fit  for him because it has even more  Attack and Piers' Mercury power (as  well as the fact he can potentially   have four  Mercury Djinn set onto him as soon as he joins) will make  the Hurricane  unleash all the more damaging. The Storm Brand can easily last a while,  and can be reliably replaced by the Mist Sabre found  in Aqua  Rock later on (or a Comet Mace if you manage to forge  it from  Stardust at the blacksmith in Yallam).

In Dark Dawn, the Storm Brand is the strongest weapon available to the player at the time it is found. However, in order to Unleash Hurricane at its highest power, Matthew and Tyrell must have Mercury Djinn set to them, as there is no Mercury Adept in your party capable of equipping the Storm Brand. Since Tyrell can later acquire the Vulcan Axe, which has a Mars-based Unleash, the player may consider equipping the Storm Brand to Matthew.