The player can create their character as male or female, any of ten races and any of twenty classes, giving 400 possible combinations requiring widely varying playing styles.
For example, a High Elven Wizard would annihilate their enemies by slinging spells at them from afar, while a Trollish Barbarian would have great difficulty learning spells and would be better off smashing everything in melee combat. During adventures, a player is likely to explore many different dungeons and complete multiple quests. Which quests the player chooses will likely depend on their character and on whether they are lawful or chaotic.
One feature of ADOM which greatly enhances its replay value is the availability of multiple endings. The standard way to defeat the forces of Chaos is to close the Chaos Gate, but if the player won the game this way and wanted a challenge, they could try to pass through the gate and defeat Andor Drakon, the Elder Chaos God. This would make them an Avatar of Order or Balance or an (Ultimate) Chaos God. (Yes, the player can win ADOM with an evil character who defeats the lord of Chaos, only to become a more powerful one.)
ADOM was written by Thomas Biskup, is currently at version 1.1.1 and can be downloaded from the official site. Although ADOM is freeware, unlike most roguelikes, its source code is not available.
Biskup didn't release the source because: