Theory

Theory (Japanese: セオリ, Seori) 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, another female Blade with whom Theory shares a bond.

Theory was designed by CHOCO, who also designed Praxis and T-elos.