"Impending N–[cost]" is a keyword that represents multiple abilities. The official rules are as follows: (a) You may choose to pay [cost] rather than pay this spell's mana cost. (b) If you chose to pay this spell's impending cost, it enters the battlefield with N time counters on it. (c) As long as this permanent has a time counter on it, if it was cast for its impending cost, it's not a creature. (d) At the beginning of your end step, if this permanent was cast for its impending cost, remove a time counter from it.