Intelligence

Intelligence (represented by the icon in-game) is the attribute that grants mana and mana regeneration. For each point of intelligence a Hero has, their maximum mana increases by 13 and their mana regeneration increases by 0.04 mana per second, meaning Heroes gain 1 mana per second for every 25 points of Intelligence. For Intelligence Heroes, every point of Intelligence increases their damage by 1.

Intelligence Heroes
Intelligence heroes tend to have a lot more active abilities than heroes of other classes; with the exception of Necrophos, all Intelligence heroes have at least three active abilities, with a large number of them having all four of their abilities being actives. Their larger mana pools and higher mana regen rates go a long way to help them use these abilities frequently. As a whole, Intelligence heroes have by far the greatest number of disabling capabilities, making them essential in most lineups. The items they build also tend to be highly caster based, since those items primarily provide Intelligence. With the exceptions of Dark Seer and Ogre Magi, all Intelligence heroes are ranged. Because Intelligence heroes mostly have abilities such as static damage nukes that do not scale, they tend to have a strong early game, when enemies' health pools are low, but a much weaker late game, when enemies have high health and strong defensive items. Because of this, they often fit into support and ganker roles.

At the moment, there are Intelligence Heroes implemented in Defense of the Ancients, and  implemented in Dota 2.

Below is a table of all heroes with intelligence as their primary attribute.