Invisible Enemies

Exploration Stage: Quiet Promenade
From: Alford Stone
Description: According to the scroll, a magical crystal hidden somewhere on the floating island empowers the witches. We need a geospyglass to observe the island more closely. Can you help me find it nearby?
Completed: Thanks! I can't see the witch in the sky even when I look through this high magnification geospyglass. The crystal is probably inert and not yet casting a spell at the moment. This is the perfect opportunity to perform the ritual and banish the witch!