Unlock Seraphic Gate When you have successfully complete the game, save when you are prompted after the credits and a new option will be unlocked at the Main menu allowing you access to the Seraphic Gate dungeon through the cleared saved game file.
Unlock Tri-Emblem: At the Seraphic Gate dungeon defeat the Iseria Queen.
Unlock Book of Riddles: At the Seraphic Gate dungeon defeat Iseria Queen 2-9 times. There are eight books in total and one will be awarded each time.
Unlock Angel Slayer: Successfully complete the Seraphic Gate dungeon by defeating Iseria Queen 10 times.
Unlock Hidden Scene: When you have successfully completed the game with the 'A' ending. There will be a scene involving Bramms and Lezard after the credits have ended.
Unlock Character Art: At the 'Voice Collection' screen unlock ALL entries for a character and then highlight that character and press Square to view their art.
Unlock Book of Riddles 1-8: Beat the Seraphic Gate 9 times (one book each time).
Unlock Angel Slayer: Every time you defeat Iseria Queen in the Seraphic Gate you'll receive a chest and 1,500,000 Exp for your Exp Orb. When you have defeated her 10 times you will unlock the Angel Slayer. All successive playthroughs after that will result in anther Angel Slayer and the Orb Exp.