Windy City Aven is a uncommon Creature — Bird Warrior card from Unknown Event (UNK), collector number UU04a.
Flying Ascend MagicCon: Chicago (If you attended MagicCon: Chicago and control ten or more permanents, you get the Windy City's blessing for the rest of the game.) Whenever this creature attacks, if you have the Windy City's blessing, create a 1/1 blue Bird creature token with flying.