The Guardian is not going to be a playable character for SSB4. She is from the game Guardian Legend. Being a retro character and the possibility to be different from other sword toters, she seems to be a possibility. She also possesses a jetpack like mechanism and could use that as part of a moveset.
<-A-> Pew Pew
A ^ Turns blade
A V badass slash
B. Stomp: Similar to Pit's side B in Brawl.
<-B-> POWER... something: Guardians pack pulses out as she accelerates at the opponent with her blade extended.
B ^ Flying :D : Guardian uses her wing pack (or Jetpack) to fly upwards.
B V downwards slash: Guardian aims for the ground as her blade spins at extreme speed.
Final Smash: stabs herself