Gate of Chaos

As Gate of Chaos enter the battlefield, choose
Chaos or Space.
Chaos - Whenever a Dragon you control attacks,
put a 5/2 Blue Chaos Knight creature token with flying, lifelink into play.
Space -Whenever a Dragon attacks, add {u}{u}{b}{b} to your mana pool. Until end of turn,
this mana doesn't empty from your mana pool as
steps and phases end.