Experience is on the primary Resources in the game, but is entirely hero-centric. It allows for heroes to advance levels and eventually become the highest level hero available, with full control over their powers and abilities.
 Effects of Experience
The most obvious effect is that you will level up, increasing the power, stats, abilities, and other such things for each hero. Gaining a level makes them more powerful, and gives them more options when it comes to entering battle or dealing with their own units.
 Ways to Gain Experience
A tome called the Tome of Knowledge will provide you with some experience. Destroying enemy heroes, units, buildings, and enemy creeps will also gain you some experience, at varying levels, depending on the difficulty of killing or destroying what you are attacking with your hero.
 When Does a Hero Gain Experience
When he uses the aforementioned Tome or when he is involved in the battle with the unit which is destroyed or killed. The more powerful the enemy or the larger the battle, the more experience is gained.