Every hero has a range of stats that define his role in a battle.

Primary stats:

Level — Affects heroes’ physical and magical damage, HP, Armour Class, Resistance to Magic. Currently the maximum level hero can reach is 90, this is in correlation with your player level, a heroes level cannot be greater than your player level.
Strength — Affects a heroes’ physical damage and HP.
Dexterity — Affects a heroes’ chance of critically striking and dodging.
Intelligence — Influences a heroes’ magical damage and chance to inflict critical damage.
Initiative — Defines the priority of a heroes’ initiative. The more initiative a hero has the earlier that character will be able to perform a move in combat
Health — Defines a hero's HP. If a hero loses all HP in battle the will die.
Rarity — This is the star level of your hero. When a hero increases in rarity they will receive a boost to all their main stats. This is also displayed to you when you increase the heroes rarity, most predominantly the heroes health will increase substantially.  

Secondary stats:

HP — Heroes’ health level. If a hero loses all his HP, he will die. HP can be restored in battle using special skills.
Physical Damage — Damage inflicted through physical combat, this damage can be decreased depending on the defenders amour value.
Magical Damage — Damage inflicted through magical attacks which can be avoided by a defenders magical fortitude.
Armor Class — Defines the level of physical damage a hero can block.
Resistance to Magic — Defines the level of magical damage a hero can block.
Resistance to the Elements — Reduces elemental damage taken in combat.
Magic Fortitude — Gives a hero a chance of avoiding magical damage.
Physical Fortitude — Allows a character the chance of avoiding physical damage.
Chance of Critical Strike — Determines that chance of your character performing a critical strike.
Critical Damage — When a hero performs a critical strike this factor determines how high that damage will be.
Dodge — Relates to the chance of your character avoiding an attack.
Initiative — This determines the order in which heroes will attack, characters with higher initiative will attack first.