Each character has a specific ultimate weapon that can be acquired by using the Celestial Mirror. When the weapon is first found, it is equipped with No AP ability. To remove this ability and empower the weapon to its full potential, you need to find 2 specific event items for each character. Upon doing so, you must then return to the Macalania Woods and use the Celestial Mirror to power up the weapon at the large spherical crystal high amid the treetops. Below is the description on how to get the weapon.
Get Auron's Ultimate Weapon Masamune
To acquire Auron's ultimate weapon, Masamune, you must acquire the Rusty Sword. This can be found on the eastern cliff of the Cavern of the Stolen Fayth in the Calm Lands. Take the Rusty Sword to the statue of Lord Mi and then on Mushroom Rock road. Clasko previously prevented access to this area. Place the Rusty Sword before the statute reveal a glyph. Touch the glyph to reveal the Masamune's secret location.
Masamune Power Up items
Item #1 (Mars Crest) - Can be found South of the Oldroad at Mi'ihen Highroad.
Item #1 (Mars Sigil) - Capture 10 monsters in 10 different species in 10 different regions.
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