You can join the Epic Expeditions in the Ancient Ruins or use Mystic Crystals to learn myriad skills and strengthen your armies!
Ancient Relic is a multi purpose structure. It serves as the place where Spells are upgraded (Spell Learning), the Spell crafter (Spell Edge} and provides access to the Campaign Clash game mode. It is the only place Mystic Crystals are gained and spent. Beyond increasing the buildings stats leveling is required in order to upgrade your Spells past a certain level limits.