The Encyclopedia Magika is the source of knowledge about the many different aspects of The Reincarnation's units, spells, items, heroes, and buildings. While this will not give you information how to play the game, it will help you know what each feature does, and may even improve your playing abilities by expanding your strategies.
In the game (on the actual game servers) and in the game portal, the original encyclopedia is quite cryptic and incomplete. The annotated encyclopedia within this wiki has many extras, such as tips from other players on how to use stuff. Enjoy!