Drinking this essence, which looks like a strange distorted fluid, grants you a Reality Marble.
*This essence grants you a peak human mind and body by the standards of Modern Era Fate universe. This means that you have a Genius intellect along with perfect memory, recall and indexing. Your body is strong enough to tear through buildings and can easily survive the same and can with training move faster than sound with matching reflexes.
*With training however you can even reach physical and mental abilities only possible in the Age of Gods allowing you to eventually stand as an equal to all but the strongest servants and mentally you may even be an equal to Leonardo Da Vinci and Sherlock Holmes etc.
*You have a total of 200 Magic Circuits of the absolute highest quality a human can possess both in Modern Era and even in the Age of Gods. Your circuits significantly surpass even the most talented members of the Blue-Blooded Barthomeloi family and even most Dragons will be found wanting and your talent in Magecraft is similarly at the peak of what humanity can achieve. At the beginning, your spells can vaporize entire buildings without effort and this can be trained up even more.
*Both the quantity and quality of magic circuits along with your enormous magical energy can be passed down to your descendants without them degrading over generations and may even increase. This shall make you desirable indeed to the mages of the Clock tower who wish for powerful children.
*This also grants you exceptional endurance and makes you an exceptional lover and sexual savant to the point that even the biggest thots in history such as Medb could be fully satisfied. You can reduced every woman into a puddle of pleasure. Have it as a freebee.
*You gain a one time customization to your appearance and regardless of what you choose you'll be a 10/10 even in the older eras.
*You possess a Magic Crest that is 3000 years old indicating that you family originated from the Era of the King of Magic. The focus of your family's magecraft, how many members there are, the spells in your crest, how loyal they are to you, their wealth and everything else about your family is completely up to you. Fanwank.
*Note that the number of circuits you possess cannot be increased naturally but there are other options that you can figure out. While your circuits cannot be increase, in defiance of the normal rules the amount of magical energy can be increased through training, magical experimentation etc as though working a muscle. Your magical energy regenerates from zero to full in 30 minutes regardless of the size of your pool.
*You may also decide whether you possess a pair of Mystic Eyes and a Sorcery Trait. However neither of them can surpass what the Modern Era's Mystic Eyes can do.
*Now we finally come to the crème de la crème of the essence, your very own personalized Reality Marble. Before we get into this, however, it should be mentioned that you have enough magical energy available to keep up your reality marble for a total of 3 days at maximum usage and more if you're conservative. This is significant as even the strongest Dead Apostle Ancestors cannot maintain the reality marble for more than one night.
*The rejection of the world on partial manifestations of your RM is significantly lowered such that Traced Noble Phantasms can lasts for weeks before disappearing and other similar benefits.
*Reality Marbles are a manifestation of a beings soul, An inner world manifested through the power of your magecraft. As such the strength and abilities of them can vary from person to person. Your soul is exceptional and so is your reality marble. Whether in terms of strength or variety or efficiency your reality marble stands at the top among the strongest reality marbles.
*You can have a cool chant or manifest it simply by saying the name or even without one.
*You can customize your reality marble as you please this once after drinking this essence. You can add whatever features you'd like to your reality marble as well as combine multiple different Canon reality marbles to make your own. However you can only do it this once and once set you can neither increase the strength nor the abilities through the essence. Only the variety and applications can be increased and improved.
*However this essence is compatible with other adventure formats like Jumpchains and CYOAs, so any RM gained from those can be combined into this essence to increase not just your own raw power but also all aspects of your Reality Marble as well as gaining all of the aspects from the ones combined.
*For example, you can take Emiya's Unlimited Blade Works and improve the strength and efficiency to the point that it can match the Gate of Babylon in power while costing less magic or even reduce the cost of tracing the weapons outside to be negligible. You can have death become meaningless while your reality marble is deployed similar to Solomon's Ars Paulina allowing you to resurrect those who died in your world. Hell, if you want you can have your Reality Marble be a memorial where Heroic Spirits live allowing you to draw the power of those Heroes into you granting you their strength and noble phantasms or simply calling their weapons to your hands in a manner similar to UBW or simply calling those Heroes to your side to fight as Servants while also allowing the powers of UBW and Ars Paulina allowing to even create your very own personal Throne of Heroes Reality Marble. If you want you can even have Crimson Moon's RM.
*There is however a limitation. While it is simple to grant you a Canon RM with increases in strength,efficiency etc where applicable, to grant you a customized RM you need the experiences that are required to grow the RM. For example to grow the Memorial RM you need to meet Heroic Spirits or at least know their stories significantly such a Emiya Tracing which allows you to know the History of the weapons intimately to the point of reproducing them or perhaps you can journey through Grand Order with the Servants and create memories with them allowing you to manifest them much easily than you would otherwise.
*Of course there are ways to bypass the journey needed to grow the RM but that will have to be figured out by the user.
*As a benefit, this grants you a form of reincarnation based immortality that allows you to reincarnate yourself over and over into different worlds of the Nasuverse such as Apocrypha or Grand Order.
*You can replace Canon characters if you wish and regardless of all else you can keep all your memories,physical abilities, experience and powers into subsequent lives without issues. However, this reincarnation is restricted to only Nasuverse.
*Your powers and abilities cannot be stolen, copied, suppressed, damaged or affected negatively against your will in any way. So feel free to punch Kiritsugu while taking his Origin Bullets to the chest, your circuits won't get destroyed. Also no matter what, nothing in your RM can harm you or go against your will in any way. Everything works as you like.