The DM’s pitch was to roll characters that were the local problem-solvers. Level 5, been adventuring in the same rural area for years, handled bandits/goblins/unruly wildlife. It was an opportunity to play odd/misfit characters for a while if we wanted to.
What we didn’t know at the time was that our merry band of Goonies were meant to die to amp up the emotional investment for the rest of the campaign. Tragedy in the 1st act, then the movie starts for real. It’s one thing to hear about the Big Bad hurting people, it’s another to care because you lost a party to them.
So the 1st party played for 2 sessions, made it to the boss fight, and started dropping. The wizard realized he wasn’t killing the Big Bad by himself so he fled, left the rural area for the local city, and explained what happened at the adventurer’s guild/tavern. Of course the players, whose characters had just died, signed up for revenge this time with “professional” properly built characters.
Returning with proper characters and the wizard sharing knowledge of traps, layout, tactics etc. we barely managed to win. The DM let the Big Bad (who was never supposed to die) be killed but he talked about “his master’s revenge” - the DM simply moved his plans for a villain “one step up”. It was still a hard fight - two died and I retired the character I had re-rolled saying it was injury. The wizard went on to be the grizzled sole survivor for the rest of the campaign and it was kind of a cool backstory for that player to work with.