Monochrome Moonstone

Once, when the world of Arluk was made, there were only a few classes of humanoids. The first were the simple humans, who lived cheerily in their many villages and cities. They were the weakest of the classes. The next class were the elves, who made their living much like the humans, only with the addition of magic. Then, there were the Shades. The most powerful of the classes, they were a mix of human, elf, and beast. They tended to live in unison with the animals of the wild, in the jungles and caves where no human or elf dared to step, for fear of them.
In Arluk, there was always a fight. A few rather benevolent Shades saw this and changed things quite a bit. They made three skills, simply called gunners, swordsmen, and mages. When a person was born, they were given a set skill. This ensured that the person could only fight in one way, but they could still learn to use the other two skills, though this would take many years to simply gain the ability to channel energy through the new source, and was therefore impractical. The Shades also made a new class of humanoid, called the Overseers. Much like their names, these were few but kept an eye on their subordinates, giving skills and taking them if called for.

After a while, the Shades plan backfired. Now they and the Overseers were being killed or trapped. Eventually, there only remained ten Shades and ten Overseers. Combining their skills, these twenty were made immortal, though after that they could no longer age or grow stronger or weaker. Each Shade was given each of the skill classes and the Overseers given two.
The ten Shades left each had an element that they were represented by. There was light, darkness, fire, water, earth, air, life, death, blood, and wild.
The Overseers followed along the same lines, though they were obviously not as powerful. Finding this, their greed took over and they trapped away each of the Shades as a mere dungeon mob.

And now, thousands of years later, the Shades wake.