Sorcery · Keystone
Passive: Damaging basic attacks, abilities, item effects, and summoner spells, as well as the application of crowd control and damage over time effects, apply stacks against enemy champions, up to one per cast instance per champion. Applying 3 stacks to a target within a 4 second period grants you 25 + (50-25)/17*(x-1) for 20 / 12.5 + (25-12.5)/17*(x-1) for 20 bonus movement speed and 50% slow resist for 3 seconds.
Adjusted in URF, Arena. Pick a mode above to see the differences.