Cap'n Kobold
Hero
Depends on the situation. If the party are definitely out, and no hope of intervention from others. If there were other/rival adventurers established in the game, I might run a one-shot where the group plays another party trying to recover the original party or beat the BBEG.
Generally a new game would be started rather than the campaign continuing with the repercussions of the BBEG's victory.
Generally a new game would be started rather than the campaign continuing with the repercussions of the BBEG's victory.