Removing all +1/+1 counters from a creature affected by this ability or removing Sigarda's Summons from the battlefield will cause that creature to revert back to what it was. Notably, this may cause a creature to lose flying after it has been declared as an attacker but before blockers are declared. This may also result in a creature with damage already marked on it being destroyed if that damage is greater than the creature's toughness.
Random a card of Magic: The Gathering (MTG), but you can also roll the D20 dice, random a Planeswalker, have fun with the random rules and more.