Meet the conditions to unlock new modes. They can be accessed in the Battle menu.

Mode	How to unlock
Arena Duels	Complete Prologue: Part 3.
Event Maps	Complete Prologue: Part 3.
Paralogues	Complete Prologue: Part 3.
Sacred Seal Forge	Complete Chapter 14 (Intermission)
Special Maps	Complete Prologue: Part 3.
Training Tower	Complete Chapter 1: Part 5.