This meme summarizes my entire DM experience

Yea but if the party knows ahead of time they're going in to fight 300 bloodthirsty cultists and goes in without much of a plan a tpk is a pretty fair outcome for that. You should give them multiple obvious paths forward to defeat them if possible, but if they just charge in like idiots they should expect to all die. Personally I wouldn't want to play in a game where that ISNT the outcome of doing something so stupid, the ultimate looming threat of a TPK is why ultra dangerous encounters feel so good to survive against. Obviously its all about context and what the players know going into these situations beforehand, but I honestly believe if there is 0 threat of death you are no longer running a game, it is just another form of railroading / artifically keeping the game alive against its will.

/r/dndmemes Thread Parent Link - i.redd.it