Races are the highest level character differentiators in the roguelike genre: they define the major characteristics which differentiate all the characters, including attributes, skills and appearance. Usually the "races" would more correctly be defined as different "species" or even "types" – golems, for example, are neither a race nor a species, but a class of magically-powered artificial beings.
Most roguelikes use classic races from Tolkien's books, like humans, elves, dwarves, trolls, etc. However, there is a growing tendency to explore different universes with a brand new stock of races. Certainly, non-fantasy themed roguelikes will generally require a different set. The races offered in a game can provide setting flavor, offer different difficulty levels, or offer qualitatively different gaming experiences (although only a few exotic races actually fulfill this last function, the most challenging to achieve and have it work well).
Several typical tolkienesque races are briefly described in this article.
There is a general tendency to include our human species in many works of fantasy, using Homo sapiens as a standard race to which others are compared. Humans usually have the most average statistics, and possess no unique abilities. They are the most common humanoid species in many game universes. Humans are normally unaligned in matters of good and evil.
High men: Elves
While humans are portrayed as average, tolkienesque elves by convention are better in most respects, from lifespan to morality and alignment. Elves are habitually the most magically empowered, and as such are often cast into wizard or druid roles. Another characteristic feature is pride or even hubris. Elves are traditionally always on the good side.
An alternate depiction is one of a race deeply connected with nature and forests in particular. Such elves are usually smaller and more similar to gnomes or smurfs.
Stout men: Dwarves
Tolkien's dwarves are also a proud race, but instead of living in harmony in nature, dwarves prefer mining and industry, and a proper axe instead of magical incantations. For this reason, they are often shown as elves' spiritual counterparts. Like humans, dwarves are usually neutral.
The original nordic dwarves are actually dark elves, and weren't said to be smaller than humans before the 13th century.
Cute: Hobbits and gnomes
This group of humanoids combines fantasy with down-to-earthness, which results in a race that is quite similar to humans. Hobbits/gnomes generally don't possess special powers or great physical might, but this is usually offset by them being simple, adorable farmers. To fit this picture, their alignment is shown as generally good.
Orcs are the standard wild, pillaging horde race in tolkienesque settings. They typically have poorer equipment, but they make up for it with their numbers and physical strength. Their appearance is often described as a mixture of human and pig-like features, such as visible tusks. By definition, they are always on the evil side, and as such directly opposite to elves.
Unlike most other races, orcs didn't exist in any mythology and were presumably invented in the 18th century by storytellers.
Giant: Trolls and ogres
These beings are described as large, brutish and dumb. They often live in forests and caves, and they don't mind eating other humanoid species, making them closer to animals than men. For this reason, only rarely are they playable in games.
According to Tolkien trolls are petrified by sunlight. Some other sources mention trolls guarding bridges demanding a bridge toll.
Trolls, like dwarves, originate from Norse mythology, and they haven't been changed much by modern authors.
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