Arcane Inception

Your spell allows you to invade the minds of up to 4 incapacitated creatures you can see. You need only see the creatures as though perceiving them from a distance of 60ft or less, such as through an arcane sensor, viewing glass, or other method, or by being able to see them within 60ft of you. Each creature you target must remain incapacitated for the entire duration of the spell including its casting time, and when you finish casting the spell, must make an Intelligence saving throw against your spell save DC. On a failure, a creature takes 3d8 psychic damage and you invade that creature's mind. All of its thoughts, experiences and memories are available to you. At your discretion, you can force that creature to make an Intelligence of Wisdom ability check to recall some piece of information or to review their accomplishments or skills against a DC of 15. If the creature succeeds at a check using a proficiency you do not possess, you can add half your proficiency bonus whenever you make an ability check that would require that proficiency for the next 8 hours.

While within a creature's mind, you can communicate with them telepathically as though you shared a language. You can create illusory landscapes and areas and populate them with creatures you or the target creature has ever seen. This mental landscape is real for the afflicted creature, allowing you to instill fears, bonds, memories, or any number of other concepts or conditions by creating scenarios that affect the creature's thoughts and memories, up to and including short-term, long-term, and permanent forms of madness.

While you invade only one creature's mind using this spell, you can change an aspect of the creature's personality three times, using one or more of following methods, if you so choose. Each time you do, the creature suffers the psychic damage of this spell again. If this psychic damage affects a creature at 0 hit points or reduces a creature to 0 hit points, the spell ends and they gain a permanent form of random madness that can only be resolved using the power of a wish spell or similar magic.  You can use the same method multiple times if you so choose. 

• You can change the creature's Intelligence, Wisdom, or Charisma ability score. When you do, roll a d6. You can reduce the creature's selected ability score by that amount or increase it by that amount divided by 3 (minimum 1, rounded down), but never above 16, and if you reduce any of the the creature's ability scores to 0 or lower, it dies. If you reduce a creature's Intelligence, Wisdom, or Charisma score below 6, it suffers an additional effect. With an Intelligence of 6 or lower, it can no longer speak any language or cast any spells. With a Wisdom of 6 or lower, it loses the ability to form short or long term memories and gains a form of permanent madness. With a Charisma of 6 or lower, it loses all proficiencies it has with skills, tools, and weapons and if it has class features or traits that require it to take an action or bonus action, it loses access to those. 
• You can reduce the creature's challenge rating or remove its class levels, if it has any. Roll a d4; you change the creature's challenge rating or class levels by that amount, to a maximum of half of their current challenge rating or character level. If the creature has a challenge rating, the DM will adjust its proficiency bonus, maximum hit points, and natural armor (if any) to match the new challenge rating as you erode its basic combat capabilities.
• You can afflict a creature with permanent clumsiness by altering its understanding of its body. You impose permanent disadvantage on its saving throws and ability checks it makes using its Strength or Dexterity ability scores. 
• You can instill a permanent fear or affinity in a creature. You can choose any object, creature, type of creature, or scenario that you can describe in 25 words or less. The creature gains a flaw where they become frightened of or charmed by the object, creature, type of creature, or scenario that you described whenever they become aware of their trigger's presence within 100ft of them. When they do so, the afflicted creature can make a Wisdom saving throw to overcome the fear or charm for 1 minute if they cannot see or hear the subject of their trigger. The DC of the saving throw is based on the specificity of the trigger you implanted. For example, if you create a trigger for beasts, which is a category of creatures, the save DC is 12. If you create a trigger for a specific kind of beast, such as rabbits or lions, the save DC is 15. If you create a trigger for a specific kind of beast with distinguishing features or situations, such as a large or larger lion or lion-like creature with white fur, the save DC is 17. If you name a specific creature, such as an infamous dragon or humanoid, the save DC is 20. The subject of the trigger must be a real creature that you or the target is aware of and knows of.

You can cause other effects you could reasonably create by altering a creature's mind at the Dungeon Master's discretion. Regardless of what you choose, any changes you induce in the creature's mind or nature can only be erased using the power of a wish spell or similarly powerful magic.