Wizards of the Coast announced that they will ban two cards in the Magic: The Gathering Pioneer format.
With the Pro Tour on its way back and Pioneer being the premiere format for Regional Championships (see “‘Magic’s’ Pro Tour“), WotC made a move to attempt to further balance the format with new bannings. They went ahead and banned both Winota, Joiner of Forces and Expressive Iteration in the Pioneer format. Winota, which had previously been a problem in the online Explorer format, was banned because it had a large share of the metagame and created frustrating scenarios where, if an opponent lacked instant-speed removal spells or countermagic, Winota could hit play and practically win a game on turn 4.
Expressive Itteration was banned in Pioneer because it allowed Izzet decks to sustain a higher than normal win rate. Also, to align Pioneer more closely with the online Explorer format, WotC banned Expressive Itteration in the Explorer format as well.
Source: ICV2