Essence of the Blank
By taking this essence, you gain but one benefit:
Your potential becomes limitless. You can learn any discipline or skillset, even if you shouldn't be capable of it, without forgetting it and practice them into mastery, no matter how many you learn. Any abilities you have from other Essences will increase where possible and develop in ways beyond their initial purposes.
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Note: He'll only have this one essence. This won't give him unlimited will power, stamina, endurance and complete resistance to all side effects. All this would give him is the ability to learn all sorts of magics, remove his limiter and let's him grow forever.
This means: He will still have his moments of insanity and is prone to mistakes but this would also make him abuse the hell out of HP magic in this fic and I might add a few crossovers with like DxD cus why not go terrorise supernaturals while bedding a few waifus...