Essence of the Devil (Chainsaw Man)

Drinking it grants you the following:

 You are now a Devil. Before any other effects apply, you now have a functionally real world peak human body, although it is no longer the only body you own. You may design it as you like, staying mostly within human limits but with some of the next parts of this essence adding to its design.

 Choose any kind of object or idea. You are now the physical (and sometimes nonphysical) embodiment of the fear of that concept. The more that concept is feared, the more powerful you are. Something innately feared by humans at their most basic, such as Darkness, known as a Primal Fear, is so obscenely powerful that it need not walk among earth, and instead enjoys near total control in the realm of Hell.

 You may optionally choose to be anywhere between a relatively unknown and untested fear, or a primal fear like the aforementioned darkness in terms of power, regardless of what concept you choose to embody, or how much it's actually feared. You may also elect to grow in strength separate from the public's fear of you.

 Unlike most other devils, you are able to switch between several different forms and aren't locked in one state or another.

 You have three forms:

 1. A Fiend: a human body owned by a devil as it walks the earth. From a technical standpoint, you are now a devil within a corpse, living in an otherwise 'dead' human body. You will probably have a number of physical traits from your devil replacing or overlapping some of your head, like Beam's shark face or Power's horns. You're largely disconnected from your body's sensations in this state, but it will still function like an ordinary human body, it just lacks a mind and is instead your vessel.

 2. A Hybrid: This is your standard but peak human body stated before, with no horns or other changes to the head like Fiends have. This form is a real human for all intents and purposes, although somewhere on your body is a Trigger, a physical method of transforming into your third form on this list. For Denji, this is a pull-start cord like that of a chainsaw. Unlike other hybrids, you are not in contract with any devil except yourself, have full control over whether or not you transform, and can do so with just a thought. This body can be trained past peak human to the insane levels shown by Quanxi or 'normal people' in the manga, such as running across an entire room in seconds and cutting everyone in your path in half with a sword at the same time.

 3. A Devil: This is where things get real. This form is limited only by your imagination and how much you're feared, although they tend to be humanoid or at least possess some human elements to them. In this form, you may express a number of abilities based on your chosen fear, such as a Bomb devil making things explode with a glance, or a Blood devil creating solid weapons out of blood. You are extremely hard to be put down by anything less than another devil, and generally are at least several orders of magnitude stronger than your human form. If you've taken a primal fear or elected to be as strong as one, you could wipe cities off the map in under a minute, and reach the other side of the world in even less. Even non-primal devils of a certain strength are practically invulnerable to anything under them, and still casual city-killers. There are some unclear rules about needing blood to 'run' as a devil, but since you're getting the premium deal of an essence, you don't absolutely need blood to survive as a devil or any of your other forms, now only using it to heal.

 In all of these forms, you may consume blood to heal, although in your Devil form your healing is ridiculously strong. As a bonus to keep you going in other worlds, enemies you attack may bleed a great deal more than they would normally, even those that normally possess no blood at all. You can toggle this on and off at will.

 All devils follow a cycle of reincarnation, as any attempt to kill them instead just puts them in Hell for a while before they return to the world. You are now part of this cycle, and indeed go to the weird infinite-doors Hell of Chainsaw Man even if killed in other realities, and can pop back into life a short while later. You will be the only devil in this Hell, unless you want to interact with the local fears.

 Speaking of contracts, you may form as many as you want with others, with the only requirement being that both sides must give something in return. Contracts allow you to lend pre-loaded abilities, directly commune with the user when requested, attack a target of the user's choice without them ever being suspected, and more.

 You may design summoning rituals others can use to get your attention, and subtly inform others of the way to contact you for contracts, but you can also simply tell when and where someone is calling for a deal with you.

 You are a master at manipulating people into unfair contracts to get what you want, and generally have strong charisma when it comes to making deals and sweet-talking people into or out of things.

 Of course, this is all toggleable, or a sliding scale, adjusting to your liking."