The Subconceptual Plane is an extremely alien plane of existence, governed by its own physical laws. Few know of its existence, and fewer still can claim to have studied it. Those who are familiar with it treat it with caution; even if the Plane is not inherently evil, there is something extremely hazardous about it to both body and mind. There is currently no way to visit the Subconceptual Plane, and doing so may not even be possible. However, it is mentioned prominently in a few places:
• The Magical Girl researcher Phyre studied the Subconceptual Plane while searching for a way to fight back against the magico Arcanos. Doing so led to remarkable discoveries, but also drove her insane.
• When extracting the Water Core, Wendy will mention that the spell Freezing Flames calls for flames from the Subconceptual Plane, and mention the dangers or delving too deep.
• While exploring the Misty Woods, you may encounter a bizarre and dangerous creature known as a Mistwalker. Isabelle makes it clear that it is unlike anything she has ever encountered before, and defeating it causes it to drop a Subconceptual Vestige. Why a creature from the Subconceptual Plane would be wandering the forest is unknown.