Quash (previously known as Breach) is an artifact that can be played after a deal is made. When played, it cancels the deal that was just made and cause all involved players to suffer the appropriate penalty for failing to make a deal.
In Cosmic Encounter Online[]
The timing of playing Quash is slightly different in Cosmic Encounter Online: instead of canceling a complete deal, it is played during the dealmaking process. This is likely due to the slightly different mechanics of online play.