I read this thread, and I was thinking to myself, "By this point, I can tell pretty well if a game is winnable." Turns out I have more to learn.
I loaded up a game with random heroes against the Ennead on Mars, and came up with Dark Watch Nightmist, Bunker, Expatriette, Visionary, and Unity. This should be tough, but doable. I burned down Set and whittled down others of the original five villains.
Then I got the hammer dropped on me. The environment and the Ennead tore apart my team, leaving only a critically wounded Expatriette and Nightmist, who had been healing herself. Three more of the Ennead had come out, leaving me facing four fully-healed villains and two moderately injured ones who were healing at an alarming rate. I closed up my tablet, thinking "Forget this!"
But I came back later. I had to know how it would end! A Meteor Storm gave me some breathing room, letting me build up cards and HP before Desert's Wrath took that away. Expatriette went down fighting, putting a dent in the villains' HP before succumbing. Now I had only DW Nightmist, who was cowering in Mist Form and trying to build up her hand (Osiris and Tefnut's incap were making that difficult).
So here's the situation: Set, Shu, Tefnut, and Nephthys were down. Atum, Geb, Isis, Nuit, and Osiris were out, all in good shape (15+ HP). Nightmist had managed to get her Amulet of the Elder Gods out, and she had around 20 HP. The environment deck was empty; Maintainance Level, Fire in the Biosphere, and two Oxygen Leaks were out.
Are you seeing where I'm going with this? My team destroyed Maintainence Level and Fire in the Biosphere, leaving two Oxygen Leaks and 13 cards in the environment trash. Nightmist deflected the first Leak onto Nuit, and the rest...
...it was glorious.
Edit: I imagine Nightmist luring the five gods into an airlock, then smiling and waving at them through the glass before punching the button and ejecting them into the void. Mm.