Trailblazer

Unique – Lead the Way: While moving, generate 7 stacks of Momentum every 0.25 seconds, granting up to 20 bonus movement speed at 100 stacks after 3.75 seconds of moving. At maximum stacks, you leave behind a path briefly that grants 15% of your total movement speed as bonus movement speed to allied champions within. Basic attacks consume all stacks. If you are melee and at maximum stacks, your next basic attack slows the target by 50% for 1 second.

Limited to 1 Momentum item.
Ranged champions do not apply the slow.