Seraphic Gate:
Beat the game and save when prompted after the credits. A new option will be unlocked at the main menu that allows access to the Seraphic Gate dungeon through the cleared saved game file.
Character art:
Unlock all entries for a character at the “Voice Collection” screen. Highlight that character, then press Square to view their art.
Tri-Emblem:
Beat the Seraphic Gate dungeon by defeating Iseria Queen to get the Tri-Emblem.
Book of Riddles:
Beat the Seraphic Gate dungeon by defeating Iseria Queen two to nine times. One book (eight total) will be awarded each time.
Angel Slayer:
Beat the Seraphic Gate dungeon by defeating Iseria Queen ten times to get the Angel Slayer.
Hidden scene:
Beat the game with the “A” ending. After the credits end, there will be a scene involving Bramms and Lezard.