A summon is a saga creature, so it works exactly like a saga: Once you reach the final chapter, and its triggered ability resolves, you have to sacrifice the saga
The abilities of Gods function as long as they're on the battlefield, regardless of whether they're creatures
As far as control decks are concerned, bring in the rest of your Duress copies as well as Blot Out
Grade: D- Emmy (Can we call her Emmy?) is the most recent of the 12+ group and like the others that came before it (in this article) Emrakul includes a way to cheat at Magic right on the card
Where as the Amethyst/Steel deck utilises magic focusing on illusions
Finally, there are some sacrifice synergies with cards like Mayhem Devil, which will get you a little bit of damage whenever you sacrifice a fetch land