Agility

Agility (represented by the icon in-game) is an Attribute that grants Armor and Attack Speed. For every point of Agility a Hero has, their Increased Attack Speed goes up by 1 and their Armor increases by 0.14. Therefore, for every 7 points of Agility, a Hero's Armor increases by 1. Agility Heroes gain additional attack damage for every point of Agility they have.

Agility Heroes
Agility Heroes tend to deal a lot of damage per second to other Heroes, and take reduced physical damage. They often fit into carry and ganker roles. Agility Heroes tend to spiral out of control with a lot of farm, because in addition to increasing their attack speed greatly, they also increase their damage. At the moment, there are Agility Heroes implemented in Defense of the Ancients, and  implemented in Dota 2.

Below is a table of all Heroes with Agility as their primary attribute.