By consuming this essence you become as ridiculously overpowered and blessed with potential and luck as the greatest of xianxia main characters. Which, if you know xianxia, is pretty damn ridiculous.
*You gain the ability to cultivate your internal energy', letting you access increasing tiers of effects and powers in-theme for wuxia and/or xianxia, the exact nature and power level of these effects depending on to what degree you have cultivated it. You may use an existing cultivation system from any xianxia novel or create your own.
*You may grant this ability to cultivate to others and teach them your system, but they are limited to their own willpower, comprehensive abilities, and talents when it comes to success. You may still use external means, such as alchemy or creating and sharing secret techniques, to help them.
*Cultivating your internal energy slows down your aging, eventually making you truly unaging. Likewise, you may eventually transcend mortal needs such as sustenance, normal rest, or needing to breathe. Your mind and soul will be able to endure immortality.
*Your talent for, and speed/ease of learning for all things related to, cultivation (including martial arts, alchemy, and creating artifacts) is beyond ludicrous. Your aptitude is the maximum possible allowable in existence and perhaps slightly beyond even that. You may slow this down when you need to or when you wish to avoid attracting attention.
*This includes your ability to make use of external cultivation aids, such as parts from mystical beasts and exotic plants and treasures. You may easily consume and gain maximum benefit from such things even without preparation, and gain even greater benefits from them with sufficient preparation and alchemical knowledge.
*Even if your cultivation system does not normally provide you with one you will still be gifted with perfect memory, including infinite storage and perfect indexing.
*Specially blessed by this Essence and the heavens, you may ignore the usual limits of your cultivation system when you wish. Mix incompatible elements, cultivate arts limited to a gender, ignore dietary/behavioral restrictions normally required of cultivators, etc.
*Your cultivation cannot be crippled'. Injuries that would destroy your cultivation normally instead temporarily wound it; you can heal in time. Any cultivation techniques that carry a risk of death if performed wrong are entirely safe for you; you may or may not succeed, but failure will never kill or permanently injure you, and you may try again.
*Your cultivation never dead-ends or gets trapped in a bottleneck. Regardless of what choices you make or what system you are in, there are no traps that leave you stuck at a given stage of cultivation forever. All setbacks are clearable with enough hard work and your foundation' is always ideally solid.
*Your willpower is truly unlimited, unbreakable, and unsurpassed, and you have a perfect sense of 'self. No amount of pain or hardship can deter you, no illusion can trap you or bind your heart or soul, and you can focus on a task for eternity if need be. Cultivation challenges that depend on strength of will or clarity of mind are auto-win for you.
*You have the luck of a top-tier xianxia protagonist. Coincidence and fate greatly favor you, mentors and training materials seem to be available whenever most needed, discovering treasures and rarities seem to be much more common for you than for other people whenever you go exploring and adventuring, and you have plot armor sufficient to survive almost anything.
*Cultivation is not for the idle, but for those who struggle and overcome challenges. Regardless of how powerful you grow you may always find things that challenge you if you make a sufficient effort to seek them out, until you finally stand among the highest of beings.