Energy is your main tool of levelling, allowing you to quest, in-turn giving you experience points to level up. Quests are undertaken simply by selecting the quest which automatically fulfills the quest once and rewards you with gold and experience points. Each quest has an influence bar, that when filled, awards you with a free skill point to spend as you please. Completing a bar will also unlock two sub-quests related to the initial quest, which, give-or-take a point, cost and reward about the same. Fulfilling these also rewards a skill point to spend.
Upon purchasing or acquiring property through monster battles, you will gain an hourly income, providing you with a set amount of gold per hour. This gold can be used to purchase heroes, items, spells, and units, all of which benefit you in different combat situations.