Yama: Races
The dungeon creatures are a fearsome lot. They are powerful in combat and are ruthless fighters. However, they require plenty of food to sustain their hunger and is poor in the art of constructions.
The dwarves are known to be great fighters and excellent in the art of constructions. However, they are a greedy bunch who loves to eat and eat. They have a fairly high birth rate and makes good mercenaries. 
Elves are excellent marksman and is a highly intelligent race. They are speedy learners and cost fairly cheap to maintain.
Humans are like parasites, they breed very fast and are able to adapt well to new environments. They make average fighters but their sheer population and intelligence to learn and make money helps them prosper and continue the spread.
Not much are known about mythical creatures. Some said they exists, some believe so, others were skeptical. From those that believed in their existence, mythical creatures are predicted to consume little and cost little to maintain, probably why they hardly ever need to leave their hiding grounds.
The orcs are fearless fighters, though terribly dumb, they make up for their stupidity with sheer hard work. They do not need much sleep and are good construction workers. However, they eat a lot and costs more to maintain.
The great thing about the undead is the ability to survive without any food. They costs little to maintain too. However, they are known to be vulnerable in combat.