The Windy City (Unknown Event PLA009a) - Common Magic: The Gathering Card

When you planeswalk here and at the beginning of your upkeep, put a flying counter on target nontoken creature you control without flying.
Whenever chaos ensues, exile target creature with flying. For as long as it remains exiled, its owner may cast it by paying rather than paying its mana cost.
When you planeswalk away from The Windy City, remove all flying counters from all creatures.