Essence of TheSpell Brain

By drinking this gently blue glowing fluid from the brain shaped bottle you gain a spell brain.

• Spell Brain: It is a spiritual brain that is your own brain that far more savant and autistic about magic in general. It does not think about anything but magic and how to keep you alive to learn more magic. Following its lead is exhilarating, and allows you cast spells with a level of mastery you yourself can never reach, because everything you learn it learns, only better when it involves magic. There isn't a conflict of identities or anything like that, the spell brain is an addition to your existence, it is you if you only taught about magic constantly, and it will keep being you, with your actual brain in charge, so do not worry about developing split personalities.

• Supernatural Magical Understanding: As a spell brain it has a masterful grasp of any spell you know. This means it knows their inner workings, the exact way they work, has the ability to replicate anything you've casted, and real world applicable theories of how to use every spell you encounter, even if you only saw them rather than casting them. The spell brain ingests all your subconscious sensory input and constantly, with a single minded focus, thinks on how to utilize and improve the spells you know. If you smell the slightest bit of gas, the spell brain will start to calculate how much gas it would take to make an explosion. If you saw a zombie movie, the spell brain will think constantly on how it would deal with a zombie outbreak, or if everyone around you suddenly transformed into zombies. And if you learn a spell to enhance your perception via seeing in the dark or seeing magic itself, the spell brain will use it on your senses without changing your vision, allowing it to see the world at a higher perception level and getting more sensory input without distracting you from your life. Lastly, the spell brain's existence enhances your own talent, even without relying on it, so you'll learn spells far easier than you could've before, and its presence makes your mind immune to negatively affected to read beyond the very surface thoughts.

• Supernatural Spell Modification: As a spell brain its grasp over your spells and magic is far beyond what you can imitate, so you can allow it to take over and modify your spells for you according to your desires. You want a spell for light to be brighter? Easily done, just expect a higher mana drain. You want an explosion spell to bounce on walls? You might first need to learn a bouncy spell but afterwards it is easily to combine it with the explosion spell. You want it to modify your fire dragon spell into a wind dragon? That might require you to learn a basic wind spell but afterwards easily done too. As long as there is a basis to rely on the spell brain can easily make any modification. It is however a bit lacking in imagination, so you need to direct it on what you want precisely. The more spells you know the easier it will be to modify other spells, however if you do not know anything about a subject, such as if you've never encountered ninjutsu but know magic, you can only imitate the former with the latter, but the more commonalities there are between the two the easier your spell brain shall grasp it. While it might take a long time you can also make conflicting spells to work together too, such as making cold and hot or holy and demonic, even if previously those were thought to be impossible.

• Supernatural Spell Book Crafting: Your spell brain has the ability to take over your body and write down any spell you know into a spell book that is learnable by anyone you deem fit. You have to select for whom or what kind of person you are making the spell book for while making it or the magic won't take. And even if you won't be thinking of the writing yourself, the process of making the spell book is time consuming, boring, and requires an active supply of mana. You can also use this to create spell scrolls, which are one time use version of the spells in item form, allowing even people without magic to cast the magics.

• Obligatory Optional Isekai Option: If you wish you can reincarnate or transmigrate or drop into any fictional or original world of your choice whenever you please. You can go into some kind of utopia or a dystopia, a world of reverse gender morals or a world where humanity has been replaced by mono-gendered warmongering fungi, anything is on the table. You can change yourself in the transfer process, like becoming younger and good looking, changing your species, granting yourself the local capabilities like walking and chewing gum at the same time, certain minor perks like ambidexterity, or the local magic.