Cutting Edge and Plume Edge are a series of Mercury-aligned Psynergy in each game in the Golden Sun series, first introduced in Golden Sun and expanded in Golden Sun: The Lost Age. Much like Psynergy such as Ragnarok and Odyssey, these do not amount to damaging elemental attacks that affect multiple enemies at a time and directly deal base damage points. Instead, they are single-target attacks deriving from the user's Attack statistic and mitigated by the target's Defense statistic, and then set bonus damage is added. Then, a comparison between the user's Mercury Power and the enemy's Mercury Resistance vaguely influences the resulting damage. Cutting Edge is introduced in the first game as the defining elemental physical attack move that Venus Adepts and Mars Adepts will attain when assigned the Swordsman class series (the Venus variation being renamed the Crusader class series in Golden Sun: Dark Dawn) with the help of Mercury Djinn, and its upgraded counterpart introduced in the second game boasts significantly higher added damage. These Psynergies are also featured on the tri-elemental Dragoon class series, and both class series can be made to appear on Mercury Adepts through specific arrangements of large numbers of Djinn.
...that Alex has a second slightly different, unused facial portrait placed in the games' code in a way that suggests he may have been planned to be a playable character at some point during development?
...that the Darksword, being the weapon with the highest attack rating increase in both The Lost Age and Dark Dawn (210), is the best weapon for any adept using only the Quick Strike Psynergy to be holding?
...that Menardi's Death Size and Karst's Death Scythe are the exact same ability in the GBA games' code but named differently between games?
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Note that this site contains SPOILERS. While templates are in place in various articles to indicate to readers that there is storyline material that players yet to complete the games may not yet know and may not yet want to know, if you haven't finished the currently-released games, then you read at your own risk.
11/24/2018: Datamining for Super Smash Bros. Ultimate confirms a total of eight Golden Sun-related Spirits, an Isaac-themed costume for the Mii Swordfighter, and both music tracks returning from previous Smash games.