Explaining religion is a complex undertaking. Rather than describe everything that is, I'm going to explain in terms of what is
most-accepted, and identify some of the outlying differences. In much the same way that worshipers of the Abrahamic God are divided into numerous, numerous denominations (Jewish, Islamic, Catholic, Protestant, and thousands of permutations of the broad categories),
you should expect to be able to tweak some of the details to suit your character's background or upbringing.
As a quick note, there
are divine beings and an Overseer of Pythonis may be able to contract with such a being. Saints and other heroic figures also exist under each of the Vis. Some Augurs have become icons to the people, as well.
Most religions in Araevis pertain to
the Vis. This is in part because the Vis have shown, and continue to show, their power. It's hard to argue against Bellator's influence when someone throws a fireball at you. It's difficult to say that Castus does not exist, when his name invokes miracles of healing and mercy, some of which cannot even be explained (like healing a demvir's mechanical body). However, beliefs differ in many ways on what that means.
The most common belief in Araevis views the Vis as a pantheon of five gods, with Castus as the Viskar, the head of that pantheon -- similar to the gods of Mount Olympus being ruled by Zeus. This belief is known as
Inlustrovis. Within it, most accept all five as gods, but choose one to devote themselves to, or at least one to aspire to, some of which is culturally biased: velen have a predilection for Serpens, who governs things like trade, while enlil lean toward Aquila, who espouses improving yourself and seeking new heights. Still, it's not racially distinct, as the southern laicar settlements in Prenditus are heavily invested in trade, and there are monasteries dedicated to Aquila. Similar to Saints in Catholocism, you can also expect people to follow different heroic figures under their chosen Vis, such as Saint Juno of Serpens.
In this belief,
the Exul, or banished ones, are similarly powerful but villainous beings. Some consider them gods, some believe they are just evil beings that wish to be gods, but there's little question of their existence or influence.
However, a much smaller, but influential group believes that only Castus is a true god, and the other Vis, while powerful, are servants to Castus -- akin to angels in the Bible. This belief is known as
Solaviskar. It is a racially biased belief, and almost -- but not entirely -- followed by laicar, typically those born into status. The belief is that only the laicar are the chosen of Castus, and the other races are servants of Castus' servants. While not typically abusive, they can be very manipulative or dismissive in their self-assured superiority. The Exul have no power that can contend with Castus, in their eyes.
There is also a transtheistic belief which believes the Vis exist, their power is real and can be drawn upon, but that the Vis do not actively meddle in the world they've created. You can compare it to the
watchmaker analogy, a school of thought around
intelligent design, which holds that there is an almighty God, or gods, who created the Earth and the universe, set the rules and laws, and sat back to watch it, rather than ruling it. In Araevis, the belief is known as
Omnevis, and it holds that the scripture and stories of the Vis are examples to live by, providers to be grateful to, yet not rulers to worship or beseech. Here, it's rare for people to believe in the Exul except as examples of what not to do, warnings against sin.
Although Demvir are not mentioned anywhere in the Annales Viskar, Natalis Viskar, or any other scriptures, they frequently have an interest in spirituality, seeking to understand their place in the world, their reason for existing, and to that end they are often believers in Inlustrovis or Omnevis.
Even though I say it's hard to argue against the existence of the Vis, when you see their power firsthand, however, there are some beliefs that do just that. A pantheistic, nature-worshipping belief known as
Essentia is considered pagan by many, but their belief is that the powers and miracles that are attributed to the Vis are, actually, powers given or miracles worked by Araevis itself, natural forces, or spirits. You can compare this to Wicca, and like Wicca, this is a relatively modern view in Araevis. Essentia does have ancient roots, however, in the form of small towns or countries following divine beings, nature sprites, daemons, or vistra of sufficient power and influence. The Exul do not exist under this belief, but other evil beings do.
Then, there are the atheists and agnostics. Known as
Vacuavi in Araevis, the atheists are a minority, but growing gradually over time due to the rapid advancement of technology, which can sometimes replicate the same abilities as spells without worship or ritual. There's no question that power exists, but there's growing evidence that the power can exist without devotion to the Vis. There are few who can actively cast spells without faith in the gods, but they do exist.
Scattered throughout the world are many smaller, dead, or forgotten religions, as well. For instance, followers of the deep lord Cete believe that the Vis existed, or perhaps still exist greatly diminished, but that their followers are clinging to dead gods, while Cete is a living, all-powerful god. The
stricken races, believing themselves forsaken by the Vis, instead embrace
the Exul, their fellow outcast gods. Stricken do not believe in mercy, and it is rare that you will find one with a healing hand.
You also have
aberrant races and
peoples in distant or remote parts of the world who do not fit into the prime races and do not feature in any of the religious works, or have been isolated from their fellows and never been taught. These are entire cultures that have never heard of the Vis, and while they may draw powers of some kind, they do so from their own gods, spirits, or what-have-you. Finally, there are mysteries with unknown origins that may have ties to other religions, such as
Adamas Cor or the
Idols of Senes.
