I’m curious what Cora and Regina want with the dagger if not to kill Rumple. I guess it makes sense that they wouldn’t want to kill him with it (since Regina or Cora would become “the Dark One”).
My guess is they want to make Rumple suffer. Force him to kill Belle or Bae.
That, or maybe they think with Rumple under their control they can combine their magic to take SB back to FTL -or maybe they want to take over the land without magic?
There is probably a reason 2×17 is a flashback episode right after they get the dagger (2×16). Maybe they force Rumple to incapacitate the town (so the SB townsfolk get stuck reliving the past)? I think it has got to be significant that the flashback is after that episode. Otherwise it seems out of place.