Virtually none of the information in this post is new, so devout followers of the blog can probably safely skip it. However, it is a condensed collection of all the most important features of Aarn that someone new to the setting would need to know first. If you are new to the setting and this blog, please enjoy.
Aarn is a planet in a solar system like any other. What distinguishes it from other earth-like planets is that half of Aarn is blanketed in magical storms, making only one hemisphere inhabitable.
The many races and civilizations of Aarn can all be categorized as "Godtouched" - inherently magical creatures whose physical abilities far outshine what we would consider possible in real life. A human on Aarn in peak physical condition would be able to leap 20 feet straight up in the air, hew a thick tree in half with a single sword stroke, and run extremely quickly in short bursts of speed, though an average human on Aarn has physical capabilities on par with the average human on Earth.
Beyond their physical abilities, godtouched races have access to three different kinds of magic. Wizardry is magic that is scientific, technological and pragmatic. Channeling is a natural magic that is similar to the super powers of people in comic books, guided by 14 different magical elements. Divine magic is creative and intuitive, a magic that is learned through prayer, meditation and self-expression.
The fey are an important group of uncivilized sentient creatures that inhabit Aarn. Fey are mysterious and do not necessarily follow the laws of mortals, though they do follow their own strictly self-imposed limitations. Although fey can be defeated in combat and even killed by mortals, the essence of a fey will be reincarnated into a new fey. This new fey will remember its past lives completely, though strangely holds no grudges against those who have wronged it in past lives. The inner mind of a fey is alien. Fey do pretend to have somewhat mortal concerns and a vaguely mortal way of thinking, but it should be remembered that they are only pretending.
Humans are the dominant godtouched race on Aarn, and they outnumber all other godtouched. However, Aarn's population of godtouched creatures (human and non-human) is quite low. This low population is largely due to a high mortality rate and violent way of life. Due to the low pouplation, most areas are plagued with massive poverty gaps. A kingdom with a robust and scientifically advanced cities might have rural areas where the technology and education levels are little better than feudal times.
The sciences and technologies of Aarn are based around magic instead of electricity, magnetism or combustion engines, but in many respects, the functions of Aarn's advanced technology is on par with ours. In the medical sciences, this technology is actually more advanced than ours. Those with access to magic have the ability to cure virtually all physical ills, and the human lifespan can be increased by several centuries with access to constant magical treatment.
The academics and intellectuals of Aarn are also aware of concepts such as bacteria and viruses, atoms, chemical reactions and advanced mathematics. Further, Aarnian scientists have developed magical items that serve the same functions as cell phones, GPS devices, holographic projectors, assault rifles, anti-gravity devices, and free energy devices. Those with access to education would know of this information, although those without access to education would remain ignorant.
Despite Aarn's advancement in magical technology, melee combat is not obsolete, mainly because all godtouched races develop a natural resistance to destructive magics. The physical prowess of godtouched races also allows them to use melee weapons in extraordinarily effective ways, as mentioned earlier.
Gunpowder firearms exist, but are poorly represented - they are inferior to magical ranged weapons, even considering the magical resistances of godtouched creatures. The physical damage caused by firearms is only on par with the damage that can be done with the enhanced physical abilities of a godtouched using a more "primitive" weapons, anyway.
The armor that is worn by adventurers tends to be comfortable and flexible. Magical light armor is more common, cheaper, and more desirable than plate mail, which is seen as uncomfortable and ornamental. Wearing plate mail does imply a certain level of societal status, though.
On the spiritual side of things, Aarn has many conflicting religions. Most of these religions are wrong, and the rest are dead wrong. The way the gods of Aarn are worshiped and represented varies widely from region to region. Many gods that are worshiped are also fictional - it is difficult to tell the difference between a god that is fake and a god that is "real." Divine magic is not strictly dependent on the patronage of a god, nor do the gods control or guide any sort of afterlife.
The only afterlife Aarn has is a series of nine hells. Each hell is an exaggeration of a certain kind of lifestyle. Depending on your tolerances, it is quite possible to find yourself in a hell you enjoy. The demons who run these hells are not trying to make you suffer, but they are not trying to make you comfortable, either. Because of how the hells are set up, the dishonesty, pride, ego, indoctrinated religious beliefs, self-hatred and guilt of many mortals cause them to find themselves in a hell where they are miserable. These hells float in the Astral Sea, a quasi-physical realm which is the original home of the gods and fey, the place where all mortal minds travel in order to dream, and the source of all magic.