In today’s Commander Rules update, Flash – the card not the mechanic – was banned. The instant has been dominating the Competitive Commander scene, known as cEDH, for its interaction with Protean Hulk and how easy it could enable a victory. Despite the ban being aimed at cEDH, Flash is being removed to the format to signal that cheating creatures into play in a non-interactive manner goes against the spirit of the format.
The rules update also tweaked rules regarding objects outside the game. The change will allow Companions to function while still limiting cards like Burning Wish or Spawnsire of Ulamog. As Companions are self-referential and do not ask you to retrieve other cards, they will be legal in Commander.