By drinking this essence you may attune your existence to any fictional world or universe you wish. Granting you many powers and abilities based on that work of fiction.
*You may switch between your attuned universe and your home universe at will, or if you have other travel powers wherever in the multiverse you currently are.
*Starting off you may choose a single franchise or particular iteration of a franchise of your choosing, giving you several options of starting choices:
*You may choose race,career, and other starting options of that universe and transform into them.
*You may choose powers, conditions, and backgrounds of a particular franchise or specific character. Such as being a force sensitive, a bleach shinigami, or having Marvel mutant powers. Or say having the money and intelligence of Bruce Wayne or the powers of Monkey D Luffy. However you only start at the initial power level they were first shown with. And can't pick exceptionally powerful beings such as skyfathers, cosmic beings, Golden Superman, ect.
*You may "summon" (more like conjure a copy of) items, vehicles, creatures, and other things of your attuned universe.These summonable objects start off as either common to the world or are objects popularly associated with the franchise in question. Blasters would be considered common items from Star Wars and Light Sabers would be popularly associated with Star Wars, despite being extremely rare in the galaxy.
*You can use any item as if you fulfill any requirements needed for the item such as mana, being a particular race,specific person, ect,, and all items and other things have an inbuilt restrictions to follow your commands and not harm you. Even just a pistol from some action movie universe will simply fail to fire if pointed at you.
*Items and objects that have downsides that negatively affect the wearer do not affect you or people you choose not to. A magic sword that controls the user or drains his life force will simply no longer do so while still having access to the powers it should still have.
*Specific items may be summoned back to the attuned if lost or stolen. Expended or broken items would have to be re-summoned.
*As your attunement grows your power and the rarity of the items you can summon and control go up as well. Attunement grows naturally over time, but can be hastened with time spent in your attuned universe, and the more you interact and affect the universe in question. Becoming an infamous pirate captain in a One Piece universe would affect the rarity of summonable items, and your overall power level.
*Also increase Attunement by cross pollinating your current universe with the "essence" of your attuned universe. This starts with just bringing over items and things Acting in a way that in accordance with your attuned universe and eventually this effect will bleed over, allowing other things such as people, powers, and even metaphysical concepts to cross over. An example would be having a One Piece style pirate crew in your original universe or the marvel universe, and eventually "wild" devil fruits may start appearing and shonen style fights become more the norm, until actual portals and mergings start to happen.
*You may perform a ritual to attune to a new franchise or universe, effectively freezing your current level of attunement with your previous universe and starting a new one.You may still use items summoned and still possess more mundane skills and abilities you have from the previous attunement. And at any time may switch back to any of your previous attunements at will.
*Starting a new attunement will not affect the level of crossover already in your current universe. And if continued may result in a truly weird world.