Question

What shape is Tibia? Is it a planet or flat earth? Are there any documents/books suggesting that Tibia is a plant/round?

Answer 1

A private theory mine that I actually think that makes sense (I guess) about Tibia's shape:

We can buy Globes at any furniture shop. It really looks like a planetary globe if you look at it!

Globe item on Tibia: 

Image source: https://www.tibiawiki.com.br/wiki/Globe

So maybe Tibians believe that they live in a globe? I think so.

Rest assured that in Ancient times, one Greek scholar almost measured the value of the sphericity of Earth, getting it wrong but not much. Many flat earthers nowadays will look for some obscure works in Middle Ages to justify the concept of it historically (there is actually a controversy on how widespread was the flat earth concept in Middle Ages among scholars). I can look for data defending it (read a long time ago about the subject), but this is just a detail that I would like to point out... Maybe Tibians believing in a globe planet is not really a far fetched guess, although I never saw any comment about it :)

Answer 2

Since Tibia is a medieval game, we have very little information of this type. I found only one mention about the planet and he was not talking about the shape it has. This mention was in the book  Manasphere which is In the Isle of the Kings Library, where the name itself already mentions a sphere.

So we don't have enough information to draw any conclusions.

Source: https://tibia.fandom.com/

Answer 3

Flat or round? Disk or orb?

Taken directly from my source: Tibia Article - Oct 04 2012 - Rich in Detail 3.0

The shape of Tibia is still under discussion by the scientific community. Some historians and theologians hold the opinion that the world is an orb. They are referring to Zathroth's treachery against Tibiasula, and the actions of Uman and Fardos after her death. The binding Tibiasula's dying body to the column of time makes them believe that the shape of Tibia is round, or at least like an ellipse, but for sure, not flat like a disk.

This is just one opinion, though. On the other hand, there are many followers of the idea that Tibia is a disk. In Liberty Bay, for example, you can find a book about the "The Lighthouse in the Middle of Nowhere" with the following content: Sailors claim to have traveled as far as the end of the world where the water pours down into nothingness. Although it is easily recognizable during daylight it poses a special threat at night. To make matters worse, a spooky lighthouse sometimes appears out of nowhere to lure ships over the edge of the world. Whether it is really a lighthouse or some other source of light differs from story to story and remains to be determined.

...The end of the world where the water pours down into nothingness... to lure ships over the edge of the world. This does not sound like Tibia is an orb. You can also have a look at the ships and their routes around Tibia. It seems that almost all routes are along the shore or between isles. Maybe, the captains do not want to risk to sail into a storm on the high sea, or they are really afraid to fall over the edge of the world.

Of course, a book is only a book, and the habits of the captains do not prove anything. Also, seamen are often ill-reputed as drunkards and storytellers. So, their reports will probably not count as evidence of a flat world.

In addition, there are arguments against this seaman's yarn, if you want to call it that way. Occasionally, new lands are discovered. The Ice Islands in the north-west, Liberty Bay in the south, or not so long ago, Quirefang in the north-east. But if we always find new lands, islands, small continents, where is the edge of the world? Where is the big waterfall, where the water flows into the void? Could it be possible that Tibia is unbelievably large so that it would take half a human life to find the end or to circumnavigate it, if it is a globe?

While talking about the historical and theological point of view you should also consider the genesis once more. A detailed study of the two suns, Fafnar and Suon might lead to a possible answer as well. Also, astronomy could help to find an answer to the question. To be serious, Spectulus does not share his knowledge easily.