Historical Rules · 1 May 2014
Rule 207.3
Official source text from the 1 May 2014 Rules release
A guild icon appears in the text box of many Ravnica® and Return to Ravnica™ block cards. These cards either have the specified guild’s exclusive mechanic or somehow relate to the two colors associated with that guild. Guild icons have no effect on game play. Similarly, a faction icon appears in the text box of most Scars of Mirrodin™ block cards. These faction icons have no effect on game play.