Content Type: Gaming Guides
Auron’s Celestial Weapon is the Masamune. Obtaining and upgrading the sword will require some exploration and doing some of the Monster Arena sidequest.
Fully upgrading the Masamune grants the passive effects Break Damage Limit, Triple Overdrive, First Strike, and Counter-Attack, and will allow Yojimbo to break the damage limit. Damage from the weapon scales off of Auron’s HP, but unlike every other Celestial Weapon in the game, the damage gets higher the lower his HP is. It will do 100% damage at 70% HP.
After gaining the Celestial Mirror, the Masamune can be found on the Mushroom Rock Road, but you must first find another weapon. Head to where the Cavern of the Stolen Fayth is, and go to the Eastern cliff. In that area you will find the Rusty Sword.
After grabbing it, go to the Djose end of Mushroom Rock Road and take the Northwestern path to find a rising platform. At the top, place the Rusty Sword at the statue of Mi’ihen, and a glyph will be revealed nearby. Interact with this Glyph, and you’ll get the Masamune.
Mars Crest and Mars Sigil Locations
The Mars Crest can be found in the Mi’ihen Highroad. In the final area that leads to Mushroom Rock Road, take the path Southeast, and follow the path all the way to the end. At the end of this passage, you’ll find a treasure chest with the Crest.
The Mars Sigil requires you to do part of the Monster Hunt side quest in the Monster Arena. You earn it by unlocking any combination of ten Arena Conquest or Species Conquest monsters.
To unlock an Arena Conquest monster, you must capture at least one of every fiend in an area, while capturing at least one of every fiend in the same species (like capturing every Flan fiend) will unlock a Species Conquest one. After unlocking ten monsters total, you will be given the Sigil as a prize.
Once you have both the Crest and Sigil, take them back to the altar in Macalania Woods to fully upgrade your Masamune.