I have twice before had a game in which, for story reasons, I wanted to kill the entire party all in one go. Once because I needed the players to enter the afterlife, the second because I wanted the players to be resurrected a while later in the future. In a "traditional" rpg where the GM is god you can simply inform the party they have been killed, but dungeon world has rules that the GM must follow.
The first time I did this I had the players ambushed in the woods by bandits and ended up playing the game as the antagonist. Seizing every opportunity to make the situation more dangerous for the players. This rather predictably was not very fun. I violated the "be a fan of the players" rule and we ended up with a very long fight sequence. Most of the players rolled last breath multiple times and it was just a complete slog.
The second time I had better luck, instead of having the party killed by ordinary characters I set up a front and had a being of unspeakable power as the antagonist. This made the build up fun and at least made their deaths feel significant. This time we were also playing the dungeon world hack Freebooters on the Frontier. This makes two changes that are useful for me: It generally makes the players weaker, and it allows me to skip the last breath roll if their corpse is unrecoverable. However I still didn’t feel like this was handled perfectly. The fight was still a little drawn out and I think the players were reasonably ticked that I gamed the system to prevent a last breath roll.
If I’d like to do this again in dungeon world, without the advantages I receive from the freebooters hack, how should I do it? Do I need to communicate to the party that I intend to kill them all for the story? How do I avoid the mechanics of the game keeping my players alive when the story requires them to die?
Maybe this story beat is just a bad fit for dungeon world, but I’m still interested in techniques that could make this less of a bad fit.