In order to gain a level your Heroes must earn experience points by playing scenarios; some scenarios reward your Heroes with an experience point and some do not. Whether you successfully complete a scenario or not, you will still gain any experience point reward it may give.
To advance from level 1 to level 2, your Heroes must earn 2 experience points. To advance from level 2 to level 3 they must earn an additional 3 experience points, and so on (an additional 4 for level 4, and an additional 5 for level 5). Each Hero gains a level at the same time; Heroes will always be the same level as each other.
Example:
At the start of the campaign there are two scenarios that will earn your Heroes an experience point: Twilight Watch and The Vault of the Ancients. Once you have played both of these scenarios, your Heroes will advance to level 2.
When you have enough experience points, you will gain a level at the start of the next City step. The following table details what happens at each level:
Level 1: Read Level 1 of your Hero Book and the Campaign Book
Level 2: Read Level 2 of your Hero Book and the Campaign Book
» Gain a new Vitality disk and a Stamina chip.
» Choose a Class from the two available for your Hero.
» Gain a Class Skill.
» Gain two Level 2 Action tokens.
» Unlock an Action slot.
» Your Hero may learn a Profession.
Level 3: Read Level 3 of your Hero Book and the Campaign Book
» Gain a new Vitality disk and a Stamina chip.
» Gain a Class Skill.
» Gain two Level 3 Action tokens.
» Unlock an open Action slot.
Level 4: Read Level 4 of your Hero Book and the Campaign Book
» Gain a new Vitality disk and a Stamina chip.
» Gain a Class Skill.
» Gain two Level 4 Action tokens.
» Unlock an Action slot.
» Gain an Inspiration gem.