Players can purchase eggs and juvenile creatures from local hunters. The next step is to set up a magical treatment to enhance the creatures’ strength, agility, and other attributes. Nearly all these traits can be manipulated with magic scrolls, potions, blood infusions, and runestones, although overuse of magic and potions can cause severe illness, infertility, decreased lifespan, or even death.

Natural species are weak and perform poorly in the arena, but all have at least one valuable ability. There are three classes of creatures available: Insectoid, Reptile, and Carnivora. Players can only crossbreed species within the same class, and the best offspring can then be selected for magic treatments to improve their combat performance. Only eggs and juvenile creatures can be treated. Adult monsters earn experience fighting in the arena and learn new skills when leveling up, but these skills are not inheritable.

There are multiple options for players to house their monsters in the various chambers and cellars of the Old Keep, or they can build a small hut or kennel in the courtyard and upgrade it. Depending on their temperature tolerance, some creatures can live in a flooded dungeon cellar while some others need a warm environment to remain healthy. Only healthy creatures can fight and earn money for their masters.