What is inside the arcane sanctuary of Final Fantasy 2?

Answer 1

Inside the Arcane Sanctuary is the mage, Deumion, guardian of the ultimate Light and Dark spells, Revive and Destroy.

Once you complete the three Arcane Labyrinth sections on the overworld map, you next visit the Arcane Sanctuary to speak to Deumion. First you must fight his summoned creature, Phrekyos. Once done, you will then give him one of the keywords you've learned as you progressed through the labyrinth, this is how you get each character's ultimate weapon.

Saying 'Hope' to him and giving him the Light of Hope item will make him give you the Revive tome. Saying 'Destruction' to him will cause you to have to fight and kill him - the reward is the Destroy tome.