Theory is a Rare Blade in Xenoblade Chronicles 2. She can grant tremendous power to her Drivers, Rex, Nia, Zeke or Mòrag, and their allies. Theory uses the ice element, wields a Chroma Katana, and acts as a Tank in battle. She moves as a skater on ice with an elegance reminiscent of a fairy, similar to Praxis, a female Blade with whom Theory shares a bond.
Lv. 1 - Ice Slash - After throwing ice knives, attack with slashes.
Lv. 2 - Frost Banish - Release a powerful somersault kick after three repeat attacks.
Lv. 3 - Rebel Sister - With one slash, smash an ice pillar and attack enemies over a wide area.
Lv. 4 - Winter's Wake - Hurl out continuous ice strikes to freeze the enemy in their tracks.
Accuracy Up - Increases accuracy.
Nullify Reaction - Nullifies one reaction.
Aerial Flashdance - Counters attack with physical damage.
Conviction - Increases damage dealt to enemies targeting user.