So, judging from the Rules Reference, it looks like you lose the game when:
QuoteA player is eliminated from the game if all of his heroes are killed, if his threat level reaches 50, or if a card effect forces his elimination.
What happens if you lose all of your heroes, but for reasons other than they are killed?
(a) What happens if you are playing the Gray Wanderer and your only hero leaves play for reasons other than death (e.g. Lost and Alone or Stinker flipping Smeagol to Gollum)?
(b) What happens if your last hero in play is killed, but you have other heroes currently (temporarily) out of play (e.g. Lost and Alone or Smeagol)?
(c) What happens if your last hero in play is killed, but you've got an ally in the discard pile from an effect that discarded but did not kill them? (e.g. Folco Boffin or Caldera)? Technically, all of your heroes have not been killed.
(d) Do you not lose if your last hero is discarded from play by an effect that does not kill them (e.g. having 0 Willpower in Stage 3B of the Redhorn Gate or getting a second copy of Bitter Cold)?
Thanks. It seems like this is potentially exploitable since undefended tacks just whiff if you don't have any heroes (barring non-damage shadow effect penalities for undefended attacks), especially since with the Grey Wanderer contract now around it seems like these sorts of situations will be much more common. I was certainly treating my Grey Wandering attempts at Redhorn Gate as auto-losses if I got two Bitter Cold conditions attached, but now I'm not so sure...