Backstory: i have personally been running a group of 5 people for about the past 7-8 months and we have formed quite the level of play since we started, full character acting, logical actions and even fully formed relationships (two characters got married to each other).
We had a wizard half-orc named Grul, A warlock tiefling named Ferulis, A fighter/cleric lady high elf named Felicity, and two barbarian gnome brothers named Dro and Moe.
These characters had spent years together, traversing dungeons, defeating eldrich and ancient horrors and looting treasure, all the party members had been killed at one point or another but had all been sucessfully revived to carry on fighting, eventually even some of them got married, namely Dro and Felicity (a really cute couple)
Things were actually going great for them all, at any point they could've stopped adventuring but simply chose not to, that was unil that fateful session that changed everything
At the time i was running Tomb of Horrors since i had they had gone through everything i threw at them with little effort so they needed a bit of a challenge and knowing it from when i went through it as a player a year prior, i knew what to expect and so did they, they were a very clever and smart group so i knew i had to make it different since most of them would expect traps and the monsters very easily, so i came up with a plan
The preface to them finding the tomb was with them learning about a VERY old foe of the party named Malaki had jumped into the yawning portal to hide from them, they naturally followed the trail and stumbled upon his old notes, leading them to the time and place he went to, the Tomb of Horrors
At a certain point in the dungeon there is a fairly good place to rest once the monsters are cleared out (About a quarter way into the dungeon) I knew the group would wait there to rest and heal up after the many traps and creatures so this became my staging area, i had them all roll perception checks, all of them failed against it, meaning i could get to work
They were kept asleep using either sleep spells or natural plants and moved to cells, their items and armour stripped away completely, leaving the only offence to the spell casters and even they happened to have their higher level spells be reduced by wards and other magics
Upon waking up they found themselves in a barely lit room, a small candle sat on a table with a note with a simple word and a hourglass slowly ticking away the time "ESCAPE". Getting to work almost immedietly they begin digging around the cell, searching for a key or rock big enough to break the door, i wish they hadn't found the rock but the gnome found a pointed rock with a 20 and picked it with a 22 so naturally they escaped
When they followed the hallways of the twisted tomb they simply found a room filled with undead of all kinds, a litteral room of death (since we obeyed older rules reguarding killing them, I.E holy water or light meaning they couldn't kill them very easily)
This was where they really had to think to survive, using a few insight checks they found ways past the undead hordes, though after a few scuffles the Tiefling was injured quite a bit, however feeling that healing would be a bit hard to come by he decided to hold off, after several rooms of traps and monsters with puzzles and outside the box thinking, they finally came to the second last room of the dungeon with one final puzzle awaiting them or so they thought, upon selecting the correct answer they were dropped into a pit below them, chains held by little pressure plates kept them above a spiked pit full of lava, a lethal trap to anyone else unlucky to fail no doubt
As they hung there wondering what was going on, a small stone panel was moved away, revealing Malaki to the party as the orchestrator behind their capture and trials (by this point Dro was very low health and so was Grul and Ferulis) he laughed and had his whole speech as the party accosted and berated him, then the truth of their situation was dropped on them like a fireball
The chains they were hanging from were connected to a bigger chain up top that was slowly bending and stretching under their combined weight, eventually it would snap unless on of them dropped into the pit to lessen the weight, if someone did they would be allowed to end this once and for all, he closes the panel as he laughs
The party begins to panic as the chain droops further an further, the heat of the lava below begining to bear down on them, they began to brainstorm what they could do, Dro suggested they use potions of heat resistance to survive, only to forget they were gone, Felicity had the idea of freezing the lava to create a platform but they had used all their previous spell slots getting here, none of them were willing to leave anyone behind, they had been through too much and had always promised they would retire as a group.
As the four of them bickered, the silent half-orc speaks up "We won't ever make it out of this without blood being spilled" he said almost choking on his words "I will let the chain loose and drop down"
The party erupted in arguments and pleas to him not to do it so they can find another way, promising that they can figure it out, the half-orc sighed as he looked at the pit below and all his friends, he wasn't about to let them die after their many adventures together, the chain was creaking softly as their time was running short
He looked at them with tears forming in his eyes and a sincerity in his voice "It was always a pleasure to be by your sides and learn so much about life and the world, you taught me to not be bitter or to persue anger instead to be kind and just…"(He used to be chaotic neutral but became lawful good) "…And to help other people, i wish you all so much hapiness"
He reached for the plate that was holding his chain up, the others beggin and crying for him to stop but it wouldn't change his mind, as his fingers touched the plate ready to push he said…" I'll see you in a better place after this" He left them with his now famous phrase "Fair travels and fair lives" before pushing the plate releasing his chain and sending him to the lava below
The group screamed and cried as they watched their friend fall to the pit, a very subtle bloop came from below as he sunk, the entire party (and table) crying for their fallen friend, after climbing back up the party found their gear and made their way to Malaki, they avenged their fallen brother, brutally, and left the Tomb feeling nothing but sorrow
They buried what items he had in a grave on the Spine of the World, a spot he had always wanted to go and see from its peak, they buried his things at the summit, his old blade marking the spot where they had laid his spirit to rest, the group travelled back to Waterdeep and parted ways shortly after, losing all heart for adventuring as the loss of their friend would never leave their hearts and minds