The original submission's one line summary said: "Morningstar is a world of epic fantasy, where Heroes fight to preserve a Golden Age of magic."
Hoepfully the following list will help you see what kinds of things you can do in the setting, and what your motivations might be, and if not, I'll explain further in a later post. Number 6 should also answer the questions about Arril, upthread.
Ten things you need to know about Morningstar:
1. It's broadly based on the ancient world (relative to its cultures) rather than broadly based on the middle ages. Cultural inspirations include Greece and Rome, India as depicted in the Vedas, The Kingdoms of Africa, ancient China and Cambodia, The great Mesoamerican empires, particularly the Inca, Maya and Aztecs. It's a bronze age setting, only the dwarves have any steel, and there is no plate mail. There are magically enhanced replacements for many missing things, however.
2. There is more magic here than in a typical setting. Magic is drawn to consciousness on this world, such that life, unlife, and every animated thing in between draws its own flavor of magic. This magic pools in places of power called Nexuses; each a unique mix of energies based on the blend of souls that attracted it. Nexuses reinforce certain types of magic and weaken others. Like attracts like, so if an area is overrun with demons, it tends to stay that way. Strengthened magics are called "signature" magic, and the weakened ones are called "countersignature". For example, in a Nexus with an "Ignan" signature fire magic is enhanced, while some other form of magic, such as "Necrotic" or "Aquan" magic is countersignature and is reduced in effect by a like amount. There are no firm rules as to which Signatures are paired with which Countersignature, allowing for widely varied places of power that will give each of them a unique twist.
3. Humans are dominant (on the surface), but only barely. There is a Fey empire called Ynnidon, a mystical dwarf empire called Kharkon which is unlike what you may have seen before, and an empire of dragons locked in a lasting civil war. The largest empire by far is Hrum Vaat- a subterranean realm with filaments that span the entire globe which encroaches on every other empire.
4. There are no Paladins. Chivalry never existed here, and so the Paladin class is replaced by the Idol; a Hero of the people with the favor of the gods. The likes of Hercules, Rama, and Gilgamesh are the inspiration for this class, which has powers based on glory, the awe of the people, and weaving Fate itself in their own favor. One such ability is Aegis- which protects the Idol from harm when he or she wears as little armor as possible.
5. Morningstar has its own flavor of Artificer which makes the Golden Age possible. While Artificers can make magic items for personal use, their greatest impact is to create constructs that serve society and do drudge work or serve as vehicles, and to contribute to the creation of Wonders- Artifact level edifices that grant their effects to large numbers of people.
6. Thraxis is part of a binary planetary system with the planet called Arril, and a magical black hole called The Wheel is equidistant between them. This system is the engine that drives the setting. Arril appears the size of a dinner plate in the sky- it positively looms over everything and causes daily eclipses. Without Arril, there would be no Wheel- It formed as a result of both worlds trying to draw magic from each other. Without the Wheel to accelerate the flow of magic, Thraxis would be a much more mundane world. It is because of the Wheel that the much smaller, and much less vibrant world of Arril suffers from a deficit of magic. It simply gets pulled away too quickly.
Arril threatens the world in many ways. As Arril's orbit approaches contact with the atmosphere of Thraxis, massive earthquakes have begun to wrack the work, cracking the earth and unleashing the denizens of the aberrant empire of Hrum Vaat to create chaos. Volcanoes spring from the sea and land, unleashing devastation and allowing creatures of fire and earth to run amock, and immense tsunamis are a daily occurance in some parts of the world. Only great magic holds society together, and no one can predict what will happen when the Wheel actually touches Thraxis' atmosphere.
Furthermore, Arril threatens Thraxis directly- as an enemy. The Mother Spirit of that world hates her sister, the Mother spirit of Thraxis, and wishes to destroy her. She has tried many times, and nearly succeeded. It's said that she created the Living Prophecy called "The Canticle of the Morning Star" to sow chaos in the many civilizations of the world. Her Lawful nature requires that she be honest, but she is ever cryptic in the Verses of this prophecy. This Prophecy can change when it is thwarted, and any written representation of its verses changes to match.
Her agents include cultists, creatures composed of the stuff of the wheel itself, and those touched by the Canticle, such as the Scriven- Mages who have the ever-changing verses of the Canticle carved into their flesh.
7. Teleportation magic is dangerous when Arril is in the Sky, unless you are travelling from one type of Nexus to a Nexus with the same Signature. If you roll a mishap, you are redirected to the center of the Wheel and are lost. Teleportation works normally when Arril is on the other side of the world.
8. Worship fuels a god's power directly. There are many gods and pantheons of gods. Native gods form pantheons which an individual Cleric pays respect to as a whole. Each pantheon is cultural, they are not typically seen as different forms of the same few beings. They are distant and manifest most frequently as forces of nature or miracles in accordance with their Domains.
Usurper Gods come from other planes, drawn by the easy power and worship energies available to them on Thraxis. They tend to make more of a show of manifestation, which is why many worship them- after all, you rarely know if a native god was even there.
Godlings are gods-on-the-rise, and include powerful demons, elder things, fey, celestials, and even mortal Zanoeen Priests- clerics who worship themselves and actually gain power from it.
9. Again, there are Construct Vehicles in Morningstar. These range from enhanced suits of armor to ships that row themselves, to golems in the forms of ferocious animals which are animated by their spirits.
10. Certain cultures in the setting have begun a magical space race. Surmising that the only way to explore Arril is to fly there the long way around, different cultures have begun developing magically powered ships to do so. This will link the setting up to a larger meta-setting called Mystic Space if a group desires to do so. Mystic space is unlike Spelljammer in that space is like our own universe's version of space (with the addition of magic), but the solutions to the problems of spaceflight are solved with magic. What this means for the setting is that there are Golden Eagle ships from the Greco-Roman Empire of Brekas that dare to fly higher every day, and immense space station-like Vimanas from India-inspired Hajir that are about to take flight.
I need to know these things. 
