One of the joys of D&D is how swingy the game is in the early levels. As a GM you learn to modulate that to keep someone from dying before they reach level two. This normally takes the form of making attacks miss, or taking a few points of damage off the attack roll. Never did I expect to save characters from rolling too well.
So backstory: New gaming group, still getting used to the game/new system. Send them off to an abandoned castle, clear out some rats, get a few coins. Decided to put an aquatic troll in the basement as a boss for them to fight later. Corridor is too narrow for it to chase them up, and it dug a tunnel to the moat so it doesn’t really care about the castle proper. Leaves a CR 5 monster lurking around for them to come back and fight later on once they’re big and strong.
Decide to roll up it’s treasure, and get a 99 on the roll. Tons of gems buried in the muck, but the big deal is they get a magic item. Roll it up randomly and get the Manual of Golems, high value item they can’t actually use for ten levels or so. Deals 6d6 damage if you try to read it, but there’s no way that they’re going to get it anytime soon, right? There’s no way the people who have played before will be dumb enough to go into a room with a troll at level one, and the new players will probably avoid a giant monster with fangs and claws, right?
One of them decided to play a bibliophile, and the moment they saw the book, they went over to grab it. Succeed on their stealth roll, don’t wake up the monster, and gets away with the book. Cleric warns that the magic is very powerful, but that’s not going to stop them. As soon as they’re out of that room, they crack it open to read. 10 hp character takes 23 damage as their brain melts out.
The irony being if they had rolled a worse treasure, or even a different treasure on that same table, they would have been fine. Heck, even with the damage they might have made it out alive. Instead the dice conspired against them and we end up with a dead halfling who was too lucky for their own good.
I’m a nice GM, and I know how much it sucks to lose a character right off the bat, so I explain the situation, and offer them a chance to reroll the treasure, and retroactively change the outcome. Party unanimously agrees, and they get a much lower roll, a few potions, and a scroll. Everyone walks away satisfied.
Still makes for a fun story. Never expected good luck to be so bad for them.