First things first

The following is pretty much all general knowledge. If you feel I've left something out, feel free to ask in the comments. Some more detail you may only know if you have the appropriate skills, so I won't necessarily post the answers here.

The world of Antaraan is flat, contained within a sphere that holds the rest of the cosmos (the heavens and the netherworld). Several continents go around the rim, with impassible mountains on the very edge. Further in towards the center is a great ocean that circles the central continent. This central continent is divided into four by great rivers that run from the ocean in towards the Spiral Sea, so named because at the exact center is a great vortex, sucking the water down into the Abyss. Suspended above this abyss is a giant mountain known as The Spire, dead rock that reaches so high into the heavens that it is used for navigation across the lands. It is unreachable by any save the birds, and the Spiral Sea is great enough that none make the attempt. Magic also appears to be disrupted around the Spire to make those means of reaching it impossible as well.

Weather is warmest near the Spire (though not "tropical" per se), and coldest towards the rim (with the mountains on the rim being truly arctic). The moon cycles every 28 days exactly, so every month is divided into 4 weeks of 7 days, (and the days of the week and months will be named as we are used to for convenience), but there are 3 extra days between February and March known as the Calibration, and the moon goes through a speedy 3-day cycle (half, full, half), and it marks the new year, the beginning of spring, and a festival of monumental proportions.

Many fantasy races are represented in Antaraan, notable exception being dragons - they are just a myth. There are wyverns (slightly larger than 2 cows) that are strong and powerful, but dumb as posts, and can't breathe fire. Intelligent races include humans, dwarves, elves, halflings, gnomes, orcs, goblins, lizardmen, gargoyles, trolls, faeries, and more, but the most common are certainly humans, followed by dwarves and elves. The central continent (and its four kingdoms) are mostly human, but there is enough trade and sea travel to make dwarves and elves not raise an eyebrow. Any of the other races would be seen as exotic, except in their homelands on the rim continents.

Magic exists and is known to exist, but can only be practiced by those with the gift for it. Clerical magic is not a separate thing, but some claim that their gift comes from a divine source. In any case, they find that they have to study just as hard as anyone else to master a spell. Magic itself is useful, but not universal or overwhelmingly powerful, and enchantment is a relatively difficult and lengthy process, so while it may not be uncommon to see a traveller casting a small spell, powerful magic items are rare, and minor magic items are expensive.

The cosmos: all the rivers of the world lead (eventually) to the Spiral Sea, and down into the abyss and the underworld, where they then flow back to the rim and are reborn beyond the mountains into the clouds. Souls are believed to have a similar cycle, and thusly burial at sea is a big deal, with big shots getting a big ceremony near the (big) vortex. Typically, they are buried in full battle gear so that they can fight off the demons on their way to reincarnation. (Truth or superstition? Only I know! Muahahahaha!) Ceremonies are held in the Spiral Sea as much to shorten the spiritual journey as to protect the casks from pirates.

Gods exist, but are not huge players in day to day activities. Religion has similar importance to what it has today.
Ishkatar is the most powerful, the overseer. God of water and the great cycle, he is the giver of life and of death, god of balance, magic, healing, and sometimes destruction. He is usually depicted as a giant with snowy white hair and beard, sitting on a throne, with the world in a crystal ball in front of him.
Tolmit is the god of the sun, and is also associated with travel, fire, law, and strength. He is depicted as an armored knight atop a horse, banner flying high, flaming sword held aloft.
Lyra is the goddess of the moon, also associated with patience, goodness, knowledge, and protection. She is depicted as a gentle mother, sometimes cradling a baby.
Kay the Wanderer is the one most often known to walk the earth, as often in the guise of an old man as in the guise of a young woman, with simple green or brown robes. He/she is associated with air, earth, nature, and luck.

There are no "bad" gods, but those roles are taken by the demons who live in the underworld. When any are specifically named, they are Demogorgon (trickery and chaos), Asmodeus (war and destruction), and Abraxas (undeath and evil magic), though there are many whose names are unknown.

Technology is early age of sail, no gunpowder or printing press. Political landscape will be addressed later.