The green Marth represents Felix, a warrior who wields a longsword and wears a green outfit.
The stage and music track represent the Venus Lighthouse, an earth-themed dungeon in Golden Sun which features the boss battle against Felix.
The Earthquake rule and POW Block item reference Felix's Venus Adept element, which specializes in earthquake attacks and abilities.
Other trivia:
This spirit's Neutral type references Felix's role in Golden Sun as a childhood friend of Isaac who later joins forces with the other antagonists in the game.
In World of Light, the Felix spirit is located in the Badlands area in the Light Realm, further referencing Felix's earth-based Venus Adept abilities.
