Star Blindness

Among wizards there is known to be a skill referred to as “opening the third eye”. This is the most basic skill a mage learns when their powers are first developing and it allows them to perceive a reality of dreams and souls that is adjacent to the physical world. This gives them a wide range of perceptive abilities, but chief of all it allows them to view the parchment upon which reality is written and learn to change the world through it.
Non-wizards, or mundanes as they are often called, cannot open their third eye. They are destined to live out their days ignorant to this realm’s mysteries and intricacies. Oblivious to the innumerable strange oddities and otherworldly denizens that populate the vast, constantly shifting realm. There is, however, one way by which a mundane may perceive this other realm. A magically concocted drug known as stardust.
Once ingested stardust expands the user’s mind considerably. When a mage uses it the effect minimally expands their awareness of the astral realm, but when a mundane consumes it their third eye is temporarily opened and they see all the strange things a mage is privy to normally. This is a mind bending experience for the mundane and a frequently sought after recreational drug for their use.
This use comes at a dangerous cost, however. Mundanes were never meant to view the reality beyond the physical world. Their minds are not adept at wielding their inner eye and forcing it open through stardust can be damaging with prolonged use.
Over-use can cause a condition known as star blindness. It is when the third eye can no longer be closed after having been forced open too frequently and for too long. Because physical reality cannot be seen when the third eye is open the victim is blinded by their own sight. Lost in a spirit world of darkness and light where they cannot perceive where they are walking or the inanimate structures surrounding them. Worse yet, astral parasites will be drawn to them, their third eye like a beacon in the darkness signaling their location and advertising their inability to defend themselves the way a wizard might.
Treatment of star blindness requires a wizard skilled in magic of the soul and knowledgeable in affairs of the astral plane. In lesser cases it can be cured, but in the most extreme cases it can be an effect the person is stuck with for the rest of their life. Forever being hunted by shadow creatures invisible to the naked eye that few can see.
No cases of a mundane developing greater magical powers from star blindness has been documented. It seems that even with their third eye forever opened they cannot comprehend what they see and conceptualize it into the language of creation and words of power.