Every expansion after the initial expansion has had a promo card with the same name as its expansion, and the Custom cards follows this trend.  However, the rules are slightly broken for Tainted Glimpses - the card is simply named Glimpses instead.  That's because there are 12 "Tainted" cards in the expansion, plus a 13th card entitled "Taint".  The image is basically a montage of the Traitor's Reach images - as Traitor's Reach cards wasn't fully revealed back then.  The effect of the spell is a simple one, and take after a particular Core magi.