Energies created by combining ether with another esper type are called synthetic energies. Celestial esper (also called sacred esper) is spontaneously generated by the heavens and infernal esper (also called profane esper) is spontaneously generated by the hells. Theological upheaval has been caused by recent experiments in an astral demesne which have shown that the vast ambient ether of the Astral Sea can be used to “spontaneously” generate any synthetic esper in any of the astral demesnes. This synthetic esper will then slowly crowd out the natural philia resulting in a demesne that behaves very similarly to the heavens or hells (except, in this case, with lycan esper). Since the heavens and hells are, geographically speaking, not much different from other demesne clusters, many have now adopted the belief that rather than some fundamentally different sort of demesne, they’re just the result of some ancient wizardry. There is not yet any significant evidence as to whether the angels and demons were an intentional part of these ancient wizards’ plans or an accidental side effect.
The process of alchemically creating synthetic energies is described above. Because celestial and infernal esper are much more efficient, they are also the most common. Celestial and infernal esper have some similar properties to agape and umbra respectively, but do not have enough in common to be used directly as agape and umbra. Instead, celestial esper can be used to invoke certain powers by chanting prayers or litanies associated with the patron who discovered them (newly discovered celestial powers can be tied to any codephrase, really, that they’re attached to prayers and litanies is mostly just a tradition). This stores a significant amount of celestial esper into a sort of soul annex which can then be burned to cast a spell without draining the esper from the caster’s own soul. This is a unique and most helpful property of celestial esper.
Infernal esper can be used to create binding circles for demons and then summon them from the hells. Demons are utterly dependent upon infernal esper to go on living and the binding circle provides them with enough to sustain themselves for a while. It is commonly thought that the binding circle imprisons the demon (including by early practitioners, hence the name “binding circle”), but in truth it allows the demon to live, and they are contained within it because to leave is death. Demons rapidly build up infernal esper inside of a binding circle, however, and before long they will be able to leave and act on their own for several hours.
The binding circle doubles as a hellmouth for the obvious reason of summoning the demon in the first place, but this means the demon can also be immediately banished back if the caster finds them disagreeable. This has led to a tradition of demons attempting to trick a diabolist into signing on to bad deals rather than simply waiting them out and then doing whatever they want. Some sloppy diabolists have been known to accidentally infuse their binding circles with too much infernal esper, however, which allows the demon to leave midway through the negotiations or even immediately. If the demon cannot deceive the diabolist into signing a bad contract and the binding circle is properly drawn, it is demonic law to accept an equitable contract. This encourages people to continue summoning demons which means the hells get to benefit from those who do so poorly.
Lycan esper is not connected to any demesnes (well, technically there is the one, but that has yet to begin spontaneously generating anything worth channeling or summoning). Its only purpose is apparently to fill someone up with so much mercurial energy that they spontaneously shapeshift and go berserk whenever ambient eros is particularly potent.
As has been mentioned earlier, mana is helpful because it can open gates to the Astral Realm, something which is otherwise impossible. It is mostly useless beyond this, but because the amount of mana required to open a gate is gigantic, the amount to bring something through even larger, and the amount to go through it to the Astral Realm is obscene, there is never a shortage of need for mana amongst anyone who deals with the Astral Realm regularly.
Xaos is omnipresent. It will occasionally spontaneously generate other esper types, and though it is extremely rare, it is occasionally observed that xaos will spontaneously concentrate within the Astral Sea and generate a new demesne of philia. It isn’t known why this happens, nor why it only ever happens in the Astral Sea or why it only does this with philia. It isn’t known why or how xaos spontaneously generates other esper types, nor can it be predicted when it will do so or in what quantities, though fortunately it almost never does so in large enough amounts to, say, suddenly flood the Spirit Realm with umbra. Xaos also spontaneously generates aberrations, which do not seem to require to have any functioning biology nor do they seem to be obligated to follow any laws of physics but their own. Each aberration is wholly unique when generated. Most of them are a species of one, and soon pass from existence entirely. Some are forever alone but also ageless or even immortal. A handful have some means of reproduction and continue on as proper races today, despite their incomprehensible physiology.
Every creature’s soul is made up of a xaos esper variant. Much like philia, eros, and agape are closely related but distinct esper types collectively called lumen, every single soul has a xaos variant esper at its core. Since each soul has a unique type of xaos esper, these types are referred to by the name of the creature in question. Not the name of the sort of creature, but the creature’s specific name, so that one might refer to Sally xaos, or Benjamin xaos, or Mr Scruffles xaos, or the like. Creatures of the same race do tend to have similar xaos variants as their soul core, however, which is why they have, for example, predictable lifespans. After a certain amount of time, exact amount depending on the variant, xaos begins to degrade into necris esper. Necris esper does not produce other esper types, so when a soul’s xaos esper has degraded into necris esper, the creature dies.
Omnipresent xaos can be channeled and its raw creative potential can, with great effort and training, be controlled enough to mutate creatures beneficially. Adding alien xaos to your soul makes you unstable both psychologically and physiologically, however, making you simultaneously more prone to disease and more prone to extremes of emotion, which may negatively impact your grasp on reality. Additionally, very large amounts of xaos are lost in the process, and since xaos is the root of all creation and does not appear to be generated by anything, spending it haphazardly is bad for reality in the long run.
Necris esper descends towards the Land of the Dead, an alternate plane similar to the Spirit Realm or Shadow Realm. Xaos that is unshielded by some kind of corporeal form (even the barely-tangible forms of spirits) is rapidly converted to necris, which drags the whole soul down to the Land of the Dead. Depending on the strength of their soul and how much xaos they have to lose, they may remain coherent for quite some time. Most of these ghosts remain coherent for at least a year even without xaos as their other esper types slowly burn out without being replenished. Those killed early and who have enough ether to maintain coherency despite no longer being contained to a physical form will still have lots of xaos remaining and become wraiths, which may haunt the mortal realm for some time until their necris builds up and drags them into the Land of the Dead. Most ghosts don’t have this much ether, however, and dissipate within minutes in the same way that ambient magic does. Without any form to contain it, esper is very shortlived, with the exception of necris and untyped xaos (meaning ambient xaos that has not become a unique xaos variant as in a soul), which for reasons unknown is immune to the usual necrosis process.
The necrified xaos souls leave behind imprints that form a sort of record. The necris remembers what kind of esper the xaos would have produced if it were still xaos and not necris, which means that it’s a sort of color negative image of the person’s soul which, with proper understanding of necris esper, can be conjured into a ghostly echo. The most iconic use of necris esper, however, is in necris-xaos bonding. By bonding untyped xaos with necris, a psuedo-soul is created. This soul has a curious property, though: The xaos remains untyped and generates esper based on the color negative produced by the necris (it even filters the color negative back into positive). By bonding untyped xaos to the necris in someone’s soul as it becomes necris, the pull towards the Land of the Dead is nullified and the person effectively remains alive (or undead) as either a wraith haunting the mortal world or, if their necris/xaos soul is bound to a corporeal form, as a corporeal undead of some kind. The only drawback is that the necris fairly rapidly corrupts the xaos. This can cause personality shifts as the new necris adds essentially random personality traits to the necris soul and also requires an influx of new xaos to stabilize the soul. The former problem can be solved by just ejecting the excess necris, but the latter requires a constant stream of new untyped xaos (unless you don’t mind slowly going insane in a similar manner as xaos mutants).