Rage

"A battle cry enrages your units in a lane, increasing their attack speed significantly for 7.5 seconds"

Rage is a Spell that roughly doubles the attack speed of friendly units in a targeted lane.

Upgrades
At level 31, the Anger Mismanagement skill is unlocked. This increases the duration of the Rage Spell by 4 seconds, bringing the total duration to 11.5 seconds.