TL;DR About The Grancrest War Record Before Delving Into The Game / Q&A

A Universe's Summary

In the beginning, the world had only the human race alongside many kinds of creatures, just like Earth. The difference in what makes this more D&D-like is when a phenomenon called "Chaos" appeared in the universe (see timeline.)

Chaos: A mysterious element appearing all over the world. When chaos converges, nature's laws will be disturbed, leading to the appearance of natural disasters and monsters alike. This is also called the chaos calamity effect.

Why limit races?
Chaos convergences, or the chaos calamity effect, would mutate the human race in several different ways. The early empires would banish these mutations to other countries; the Halflings to the Shire, the dwarves exiled to the mountains, or the elves left in the forest as they were seen as abominations. These races are also very young, having existed on Atalan for only 600 years.

Why limit classes?
Unlike most 5e games, there are not multiple deities. There is not a clear "light" or "dark" side. There is no "arcane" to draw upon naturally or the general magic that you would typically know that is in this universe. Instead, there is chaos, and what comes from chaos.

Lords are based on crests, which uses chaos and is manipulated to the point where it is designed to reject chaos. This is also a reason why crests are so important and why the Grancrest is seen as the penultimate solution to stopping chaos.

Mages are based on stabilizing and manipulating chaos to their whims. They also take the archetype of being the 5e equivalent of a "bard," whereas their university training focuses them to be natural advisers to lords.

Witches are similar to mages on manipulating chaos. However, they did not go to Eramu or a university. Instead, as children, they were hidden and stowed away from any lords who sought to send them to the magical capital. Witches are called witches due to the Order of the Crest believing them to be "evil" and an abomination to the natural laws of the world. They are more free then mages, can cast more magic, and can draw from other dimensions to summon otherworldly creatures.

Crest Artists are those who imbues chaos into their body and turn it into a benefit to greater their combat potential. In short, they make an art out of the chaos they use. While chaos artists is a term you may use, crest artists is the term used due to the crest-like shape that forms on their bodies.

Crest priests or priestesses are those from the Order of the Crest, who are granted crests blessed by the Grand Archbishop of the order. Due to the blessed crests, the priests and priestesses do not believe they are using chaos, but instead a pure form of energy that had been created by Lord Leon himself, who granted it to the first Grand Archbishop to create the religious order.

Normal 5e fighter classes are those who seek not to use chaos at all on their bodies. Due to this, the commoners see these fighters as the common champion of the people. These fighters are trusted by lords to be officers in armies, or to be a cheaper alternative to fighting another lord's own crest artists if their funds are low.

Lastly, shadow rogues are those who draw from the second most common dimension aside from the chaos; their power comes from manipulating the shadow realm. When chaos converges, shadow is sure to follow. Even when chaos is not present, shadow rogues who have been officially recognized by lords would be called a chamberlain, and would be the confidant and personal body guard to their respective lords. Rarely does a shadow rogue venture out of their place as lords, rival or not to each other, unite together to hunt down independent shadow rogues who are powerful enough to be assassins.