Training is the process of increasing the Level of one of your Creatures. All of your Goblins, and non-Combat Creatures cannot be Trained. Training a Creature requires Resources and time per Level. The amount of Resources varies by Creature, and will increase and/or the type of resources required will change every 10 levels. The Training time will also increase as Creatures gain levels, but this increase can be less noticeable between tiers depending on the Creature. The Resources required for Training can be found in the Wiki page for each Creature or on the Creatures training summary page. Training increases both a Creature's combat statistics and its upkeep per hour by 20%. At higher levels this often requires players to balance the two for optimal performance.
Early in the game, most Creatures will only require a Proving Ground to Train. Some higher Tiered Creatures immediately require an Arena. Also, as Creatures are Trained beyond Level 100, the Arena becomes more widely used, and the Spellcasting Chamber will be required for Training some Creatures.
Initially, Creatures will only be able to Train to level 10. To Train to higher Levels, Creature-specific furniture must be Crafted and placed in the appropriate Room to increase the Creature's Leveling capacity. Crafting multiple instances of the same piece of Furniture will compound. Crafting three pieces that Increase the Trainable Level by 10, will allow a Creature's max Level increase form 10 to a possible 40. There is no maximum Level for Creatures, players may Train them as high as they would like, if they can provide Training Resources, and keep them happy through Pay Days.
Creatures all take on roles in battle. These specializations include Protector, DPS, and Supporter. These roles became more important after changes to the Combat artificial intelligence. Since Creatures take on these different Roles, their statistics will increase in different categories, at different Rates. However, some statistics do not increase through Training.