Complete the indicated floor, then obtain the required card to unlock the lock panel.
Bomber: Open the lock panel on Bifrost Floor 6 and defeat him in a duel.
Bruno Borreli: Complete Niflheimr Floor 4.
Dark Signer Carly: Open the lock panel on Yggdrasil Entrance and defeat her in a duel.
Dark Signer Demark: Open the lock panel on Bifrost Floor 4 and defeat him in a duel
Dark Signer Kiryu: Open the lock panel on Bifrost Floor 7 and defeat him in a duel.
Dark Signer Misty: Open the lock panel on Bifrost Floor 7 and defeat her in a duel.
Dark Signer Rudgar: Open the lock panel on Yggdrasil Floor 2 and defeat him in a duel.
Sherry Leblanc: Complete Niflheimr Floor 2.