The Dragonic Geode is an unusable Key Item in the story of Luminous Arc.
The Dragonic Geode appears after the Trial battle against the Witches. Claire reveals that she send Lucia to get it so they can heal Theo from Vanessa's Transformation Rune. The group decides to follow and end up rescuing Lucia. Afterwards they give it to Theo so he can control his Rym Transformation.