2016-11-08 : Causing an opponent to lose the game after you've announced that you're casting a spell with undaunted and determined its total cost won't cause you to have to pay more mana.

2016-11-08 : Effects that reduce what you pay to cast a spell don't affect its mana value.

2016-11-08 : You can't cast Curtains' Call without two creatures to target. If one becomes an illegal target after you've cast Curtains' Call, the other will still be destroyed.