We had a scary moment on an Armed and Dangerous on our third game vs. the challenge, that card just revealing recklessly like that when he had 3 devices and all his traps in there, one device got played by a trap resolving and we started to realize that we could very well lose on that card despite how well we had shut him down to that point.
reveal-reveal-reveal-trap-damage-shuffle-play-reveal-reveal-trap-damage-shuffle-play. . .
Fortunately we hit a run and gun on the third and shuffled his devices back in, and then finally found one. A second armed and Dangerous there would have been absolutely crazy.
And if you somehow pull of all devices out of the deck an Armed and Dangerous is an insta-loss. Good thing that is hard to do, just don't go Savage Mana crazy.
We've played:
Grand Warlord Voss: the three cards on flip was rough, but we were able to clear the field and after that he never flipped again. If you let him flip back you can get into trouble.
Omnitron: I think this one would actually be better for Cosmic, it only came into play once in the game.
Cosmitron: If anyone ever wins this with 5 heroes and (H)=10 they get a trophy, when his character card deals 9 energy damage to the 8 hero targets with the highest HP, let alone the 8 components to start the game. You cannot flip him and live, and then the Automaton Drones have 10hp. Three players it was too hard to be fun, more was just insane.
Kismet: Love it, just a great addition to the deck, and made her legitimately hard unless you Parse/Visionary her.
Spite: Was much improved, still wasn't worth saving the victims but the burn to flip and don't bother attacking doesn't work, and that is great. Under pressure from the very start, and it kept up throughout the fight.
Matriarch: Ouch. Really tough fight.
Akash,