Historical Rules · 1 July 2012
Rule 207.3
Official source text from the 1 July 2012 Rules release
A guild icon appears in the text box of many _Ravnica_(R) 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_(TM) block cards. These faction icons have no effect on game play.