Essence of the Fae Lord
By drinking this Essence, you become the embodiment, original source, and lord of all fae.
You instantly learn everything there is on fae. Each individual 'species' of fae, what they're called in every language, their behaviors, how their minds, bodies, souls, magic, etc work, how they're perceived by nonfae, and much more, as long as it covers fae. This applies to each and every universe where there is fae.
You gain perfect control of all fae, no matter how powerful. This includes godlike ones that created entire worlds or universes, fae that are the source of magic, and any fae rulers, whether they rule over other fae or over nonfae. You can change how they behave and think. Turn vicious, bloodthirsty pixies into playful yet kind beings, turn pompous elves into a humble folk, or turn gnomes into actually terrifying creatures. It's completely impossible for any fae to resist you in any way or in any capacity. Not to mention fae courts. You can instantly create any number of fae courts and maintain control over all of them. Determine the rules, how much they can bent, penalties and punishments for breaking them, the mindset of each court, and the relationships between them.
You become the ruler of any and all fae realms. Where fae live, roam, play and stay, you become not just the de facto ruler of the fae there, but also the realm itself. You control and determine the weather, the flora and fauna, any phenomena or strange properties of the realm. Do the classic and bind any nonfae to your realm for eating offered food, do the opposite and permanently ban someone for starting a simple campfire, maybe make someone's crying cause the realm to get flooded, it's all up to you.
And of course, you become fae yourself. You get automatic perfect immortality and invincibility. You lose all your personal weaknesses and become immune to any weaknesses of any and every kind of fae. Your mind receives perfect memory and emotion control, as well as unlimited creativity. Design and alter your body in any way you like, as long it resembles fae in some way, whatever that means to you. You can produce any kind of biological magical material like healing tears, fairy dust from your wings, poisonous blood, etcetera. Should you decide to have children, you can decide how they're born, if you'd rather forego pregnancy, and predetermine any supernatural qualities they'll inherit from you or the other parent if there is one.
To trick silly fools into accepting deals if you wish to be that kind of fae, you have unlimited charisma. Not only that, but your deals have no limits, drawbacks, or weaknesses themselves. You can trick gods into destroying the world they put so much time and care into creating or narcissistic trillionaires into donating every penny they ever earned. And for deals that require you to offer something in return if the person fulfills it, you are under no obligation to actually hold up your end of it, if you decide not to. And should you hold your end of the deal, nothing stops you from twisting what you give the other person. If you are a kind and honest fae, you'll always be able to fulfill your end of the deal perfectly. All of this goes for wishes as well.
Since fae are largely magical nature spirits, you gain immediate perfect proficiency with any and all nature magic. Create storms that destroy entire worlds, diseases that can kill every animal and ONLY animals, leaving people to live on a planet with only themselves and the aftermath of such an intense and quick mass extinction event, or be kind and create fungi that can cure any illness and ailment. Summon any kind of magical beasts, such as unicorns, at any level of strength. Terraform an entire planet.