Intelligence is a stat in Defense of the Ancients and Dota 2. It deals with mana and mana regeneration. Because of it's inability to scale into the late game (as a hero only needs so much mana, while attack speed and health are very powerful), Intelligence heroes have a tendency to be less effective as the game drags on. Intelligence heroes are generally burst mages, who rely heavily on their spells to deal damage. Because skills do not scale with Intelligence, the base damage for most spells are higher than an Agility heroes'. This makes Intelligence heroes much stronger in the early and mid game.
Each point of Intelligence gives 13 mana and 0.04 mana regen per second.