Caves of Qud has a reputation system that allows you to curry favor with certain Factions at the cost of others. Having a high reputation gives you perks such as having faction members become friendly, or they will graciously teach you a skill. Having negative reputation will cause those faction members to attack.
Water as Currency
Fresh water is rare and is used to barter for items besides satiating your thirst. The majority of water the player will come across in their journey will be salty water. Water also has a significant amount of weight, forcing the player to consider how much to keep on hand. Fresh water is such an important liquid it is often used in the Water Ritual.
Secrets as Currency
Another thing the player can sell is information. Certain Factions want to learn about certain topics, and they are also willing to tell the player about certain topics. This sharing is done during the Water Ritual.
The Water Ritual
Your thirst is mine, my water is yours.
Speaking to a Unique Creature or a legendary creature will grant the player the option to perform the sacred water ritual. During the ritual the player and the other creature will become water-bonded, and the player will be able to sell and trade secrets for reputation, which can be used to acquire secrets of their own, or certain skills and items that the other creature has. It is a sacred ritual, so breaking this oath is looked down upon by all factions.
Genotypes and Subtypes
As part of character creation, the player is guided to choose from among two "genotypes" - Mutated Human or True Kin. After choosing a genotype, the player will also need to select a "subtype". For Mutated Humans, the subtypes are referred to as "callings". For True Kin, the subtypes are referred to as "castes". These subtypes affect a player's starting equipment, attributes, skills, and other miscellaneous bonuses.
Radical Bodily Autonomy
There's a fable about a mimic who seeks to belong but never does, whose ambition ultimately leads to a grisly fate. Its moral serves an ideological function: to keep us from belonging where we already do. So let me say to you now: belong, friend. We wait for you joyously.
As a character's power grows, so does their ability to alter the shape and functionality of their body. Mutated Humans can start with a wide variety of mutant abilities and features, from an extra pair of legs to the power to tear open the fabric of space-time. Mutation Points gained every level can be spent to strengthen existing mutations or saved up to buy a new random mutation. True Kin can start with cybernetic implants, such as carbide hand bones to strengthen their punches or night-vision implants to better see the innumerable threats down in the caves of Qud. Cybernetics Credit Wedges and Becoming Nooks found during exploration allow them to install more and greater implants for countless esoteric purposes and occasions. Given luck and patience, a successful high-level character can be almost completely unrecognizable from the humble figure who once set out from their starting village.
Some characters will gain access to more obscure methods of reshaping their being. The various factions of Qud have different philosophies and approaches towards the mutable nature of the self. Through reputation manipulation and the water ritual, for example, Seekers of the Sightless Way can reveal secrets of the darkling star and the telepath mind, and Slog can pass down the knowledge of the Cloaca Surprise. No two characters will trace the same path through Qud. The path shapes you just as you shape the path.
Much of the world of Caves of Qud is procedurally generated. Many villages, locations, creatures, as well as the entire history of the sultans, including key events in sultans' lives, and historic sites related to those sultans, are developed through a complex procedural process.
Attributes and Modifiers
Conflict, usually manifesting in the form of combat, is practically unavoidable. Different factions have different reasons for fighting: Some fight to defend their homes, some fight to destroy other factions, and some even fight for a better world.
Caves of Qud is a roguelike, which means the default option enabled is to have the player's save wiped after the character dies, forcing them to start over.