Question Faux-Wiz

First thing to note is that spirits do not function on Essence.

Energy types:

Psychic (Psionic energy): used by baseline psychics, mutant TK, PK, ESPers, Empaths, and Telepaths; this energy pool is both internal and external to the body... the aura, the pranic sheath... created by the mental ability of sentient minds. It is a powerful, but subtle energy. Psi energy is limited in the same way that 'stamina' is limited. One typically becomes too fatigued to continue before actually depleting it... and actually depleting what you have is likely to kill you. Normal rest and sustenance, augmented by meditation, will allow it to recover. The base amount available varies, accessing it is mostly a matter of awareness and discipline. Training can expand how much is available to you.

Magic (Essence): Essence is typically an external power, extremely subtle. In its natural state it is generated in places of high concept (where there is enormous amounts of life, life Essence will form. where water is seen in all its nature, Water Essence will form) and flows through lines/channels to places of 'low concept' or void. The more Essence travels in the lines, the less attuned to its foundation nature it becomes Volatile and more 'expressive' (it reacts with the natural order of the world around it)... in this form it is considered Raw Essence. While magical beings are naturally able to draw on this Raw Essence (and higher magic beings like Dragons or the Sidhe can actually pull Essence directly from their most volatile places - the Ley Lines), humans don't normally do so. Ancient magic exists, however, that allows humans to initiate this ability within themselves... a process called "Lighting the Well" or "Sparking the Well" ... this process is not unlike priming a pump. Once a certain amount of Essence is compressed within this place within an individual (their Well), they naturally begin to draw a small amount of Raw Essence into their Well on a continuing basis. Discipline allows them to hold this Essence in their Well, and while it is there, it is 'tamed' and becomes their own. Once the Essence is theirs, they can use it to craft spells and empower rituals and ceremonies. Mutants with the Wizard trait inherently have some of the same ability as magical beings... their Wells automatically (from the moment of manifesting) begin to draw Essence at high rates, high enough that above the first couple ranks, their Wells will spontaneously Spark/Light.

Spirit (Quintessence): As Essence is in the physical world, there exists another form of energy within the spirit realms and is required for the health/life of the beings who live and make their homes in those realms. It is this power that fuels many of their abilities, though it is possible for spirit beings to also understand and work with Essence. However, these two energies are not the same... and it is far simpler to trade them than to convert them (though conversion is possible, if inefficient). It is far easier to find someone who can work with and gather both types and trade one sort for the other in much the way that common ceremonies allow for trade of attuned Essence types (ie trading raw Essence to a being from the Fire planes in exchange for Fire Essence to fuel a powerful flame spell). Baseline humans do not typically have any awareness or ability to work with Spirit energies, the exception being certain shamanic practices (most use Essence... but a rare few use Spirit). Mutant Avatars, however, have a place within their metadimension nature where a spirit can hide adjacent to the physical world... that generates spirit energy at a high rate. Normally, beings from the spirit realms cannot come to the physical world... and if they do, there is a high cost in spirit energy to get here... and a continuing cost to remain. Should they not return to the spirit realms before their energy is depleted, it can destroy them. There are places in the physical realm where they can hide from this constant drain... these are called hallows. As it happens, the place within an Avatar also acts as a hallow. This gives the spirit being a place to to be safe within the physical world, energy to grow and become more p owerful than might otherwise be possible... and an ally to help serve their cause/purpose. That makes the interaction with an avatar pretty valuable to a spirit being... which is why they are willing to expand a lot of energy up front to grant abilities to the Avatar to help them stay safe and act on the spirit's behalf.

Divine: Beyond the realm of spirits, there are also those who have reached divinity. And like spirits or mages... there is a sort of energy available to them that they can use to sustain themselves in immortality and to act to their own purposes. This divine energy is created through actions and natural dynamics (like conflict). A given god or goddess can draw on any divine essence attuned to their nature (or domain). divine energy created through the prayer of creation at a forge by a blacksmith would feed a god like Hephaestus. Blood sacrifice in war on a battlefield would be able to be consumed by Aries. Or the Morrigan. The greater the domain and more 'worshippers' involved, the more likely there are active gods 'feeding' on that energy. With lesser domains, it is likely that older gods are replaced by similar ones in newer pantheons... though one being can also move from pantheon to pantheon, using many names. As with spirits... divine energy doesn't readily convert to spirit energy or Essence... but some gods are proficient and able to use more than one, so trade is always possible. Divine energy is generally not something you can tap without already being a god... however, it IS necessary to become a god. So... you can see that there has to be some 'trick' to making that leap... not unlike the one for becoming a mage. It's also possible to fall from divinity... though if they don't do anything except sustain themselves in immortality, it can take a LONG time for a god to run out of energy even if they no longer have a viable domain or access to it.

As to what an Avatar can do to a manifesting mutant?

A lot.

Most of the energy involved in Manifesting is energy that works on a metaphysical level... remapping the higher dimensional being of the individual. That's where spirits naturally exist and much of that energy is the same sort of stuff they live on. So a 'savvy' spirit can help fill in the 'database' entries while the manifestation occurs. A less savvy spirit just supplies entries that are part of its own nature. That might be intentional... it might be accidental. After all, they're cozying up to that metaphysical data while curling up in that hallow, their meta-data pushing against the walls where the mutant's meta-data is forming. That's why you typically see more 'tailored' power sets on more 'conscious' or intelligent spirits (and they're the exception to the rule)... while more animalistic or empathic vs intelligent spirits, the avatar tends to get an imprint of that spirits own nature.

As to how much specifically? It's a matter of power. The spirit wants to benefit from bonding with the Avatar. that means they want to be getting more energy from the hallow than they are putting into powering the Avatar. So most of what they are going to do is typically going to be what they can do with the energy of manifesting. Constant high power actions later on have to be powered by the spirit. But if they're smart enough, they can copy the process of other power traits. They can give their Avatar the same strength and speed as an Exemplar. Or the blasts of an Energizer. If they do it that way, though, the power traits are typically going to be measured as separate traits... because they aren't going to go away if the spirit is lost/leaves. The only powers that will be lost when a spirit is lost, are those that the spirit is maintaining... and the most of those that exist, the more energy the spirit needs from the hallow to sustain themselves and grow stronger. The stronger the Avatar is, the more spirit energy they create. The 'bigger' the spirit is, the more it takes them to sustain themselves... unique named spirits like Kodiak are 'enormous' and consume a 'ton' of spirit energy.

A spirit that also knows magic and can draw Essence is more likely to teach the avatar magic and train them like a baseline mage. Or make them a Wiz mutant during manifestation... than to constantly feed the Avatar Essence while bonded. The former would only need to commit Essence to Lighting the Avatar's Well and then just training them. The latter would cost energy during manifesting but then would be a Wiz mage. Having to constantly provide Essence to an Avatar would be a constant depletion on the spirit... and an inefficient one at that.

Well.. .first you have to keep in mind that mutants are a human phenomenon. Humans who become Sidhe do so during manifestation... and they become Sidhe. Now, there are mutant Exemplar that "look" like Sidhe... that's a factor of their BIT. But they aren't Sidhe. Those who do become Sidhe, become Sidhe with all that entails... and that means they are no longer mutants (and don't have any mutant traits).

What Sidhe DO have... is an inherently better 'baseline' physicality and mental ability. They aren't Exemplar, they don't have BITs... Sidhe are simply stronger, quicker, smarter, etc than humans. Sidhe also have inherent abilities with magic that humans do not. Sidhe don't require a Well to filter raw Essence... nor do they have to 'hold' Essence before they can craft spells with it. That doesn't mean all Sidhe are mages... but if they are so inclined, they have enormous advantages over humans at becoming mages. Of course, this comes with a down side... Sidhe 'biology' is not purely organic... they are fundamentally 'made' of Essence. This can be tapped for spellwork, at great risk... but also means that in places with low (or an absence of) Essence; Sidhe can 'bleed out'. Which is why any Sidhe left around when the Sundering happened... died. And why Sidhe didn't just come back and repopulate the place. They literally couldn't live here any more. Many Sidhe are naturally about to host/bond with a spirit (like a human mutant Avatar... though the relationship is different - larger better protected hallow, but not the same sort of energy source feeding the spirit - a Sidhe's bonded spirit still needs to keep ties with the spirit realm to sustain themselves). Finally, some Sidhe have some innate Psi ability... typically the nobles and royals... but occasionally others. Note: this is NOT a glamour. It is just PSI... mental power... and usually either an ESP type, Telepathy or Empathy... TK is rare. Sidhe aren't PK's. Court Sidhe children benefit from lost/ancient world magic that automatically provides some Psi oriented defense mechanism to protect them until they come of age. That's NOT an inherent power and they lose it at adulthood. However, if the Sidhe does have Psi, the glamour tends to manifest in ways that translate over to their own power.

Finally... there's a lot of confusion (recurring confusion) that comes up when people talk Avatar spirits. The most important thing to be aware of is that 'sentient intelligent' spirits are NOT the norm. When a sentient, intelligent spirit bonds with a mutant Avatar, they are almost always going to do so with either a Channeler (so that they keep their consciousness safe and separate from the Avatar) or a Paladin (in which they bond a 'shard' of their total nature that they can afford to lose). Animal spirits. Minor elemental spirits. Those are the majority (the VAST majority... like > 90%) of spirits that bond to mutant Avatars. Not named spirits. Not totems or archetypes or powers. Not powerful magical beings who once lived and now reside in the spirit realms for centuries... or eras. Those things have their own complex metadimensional nature that is far too 'large' and complex to fit into the Hallow of some little mutant. And if they did? What happens to spirits that are bonded to Avatars for a lifetime... a bond at the soul level with a mortal being? There is no ancient Sidhe spirit that is bonding to an Avatar (or a modern day Sidhe). A 'shard' of part of an ancient Queen's power bonded to a newly manifested Sidhe. A powerful healer mage from the Courts set up legacy magic to bind him to a worthy successor... and then shaved off a tiny shard of his nature and sent it out as the 'precursor' bond. Feral, Kayda, and others... are Channelers or Paladins... bonded but not hosting powerful beings.

And let's face it... if most of these powerful ancients bonded with the mind and spirit of a contemporary teenager at manifestation as a mutant? They'd crush the fledgling mind that barely grasps abstract thinking with a highly developed mind, intellect and mental discipline. The idea of taking a backseat role to a child would be... hilarious. Even to the most moral of them.