So when I graduated from high school I pretty much lost my D&D group as we all took our separate ways.
Going into college I started searching for a new group, and found a classmate who was interested in learning to play TRPGs and had some friends he could introduce me to.
This party was composed of: Me (Wizards), My friend (DM), Hexblade, Ninja, Druid and Cleric (all of DMs friends who are part of this particular story).
Years later after I taught all of them how to play, DM tells me he wants to narrate a story in a world he's been building the last few years. Being a little tired of DMing by myself I gladly welcomed the opportunity.
Hexblade used to complaint that I wouldn't allow evil PCs in the party, mostly due to my lack of experience introducing such characters into the story of "saving the world" I used to run, but also because I knew the kind of murderhobbo he would become if given that chance. So for this game I decided to play myself an evil wizard obsessed with arcane power, who murdered his own master for his spellbook, mostly to show Hexblade how evil PCs should be played without turning into a Murderhobbo.
As if it meant anything, I had little to no chance to RP my evilness in such a cruel and merciless world as this.
I play nice as a DM, I balance my encounters to make them challenging but fair, I avoid killing players as I really don't care for such a thing, I even dismiss PCs with nice "he went back to his family seeing the adventuring life was not for him" or stuff like that when the players ask me to make new PCs.
DM did not play nice.
First session he explains how all of us travelled from the mainland to this island for various reasons and one way or another we are all stuck with only out starting equipment and no money to pay for a ride back home. First thing we all have to do: roll Fortitude DC to struggle against hunger since we haven't eaten in days. Dang…
Next we start meeting each other and the party finally unites to fight a tribe of orcs that's been creating troubles for the other communities in this island.
Have you ever heard the term "Death Master"? It is used for a GM who will make the party suffer and struggle against horrible odds and often kill the party only to his amusement. DM was this guy.
Our first battle involved so many orcs we barely made it only to learn that another hoard was moving towards us, we were level 1 mind you. So we had to hide. That was Session 1, we were left seriously low on HP afterwards.
Next session Cleric tells us he doesn't like the build he made and he is playing a Ranger now, as we travel through the land we meet up cleric and when we are choosing how to react to this new PC (this is a hostile island after all). The DM says:
Cleric is suddenly struck in the middle of the chest by a javelin, it was a critical hit and she's under -15 hp now. This was 3.5 so -10 meant death and back then there were no death saves.
We fought a bunch of orcs once again, barely making it out alive. By this session something that had happened back in the first battle and no one noticed is happening again: all enemies always have "1 HP" left after we finish attacking them by concentrated fire, DM says this every time as "You won't believe me but you left him at 1HP" and then the creature proceeded to attack. Now I know some DMs fudge die rolls or change stats on the fly, and sometimes you know and sometimes you as a player don't realize this. But I'm not exaggerating: ALL OF HIS CREATURES DID THIS. What are the odds?
About two sessions latter Druid informs us that he will make himself a dwarven fighter to better tank against this onslaught of monsters. We've all been coming up with ways to avoid our own deaths, I've made myself excellent friend with my levitation spell to avoid combat damage (since all these orcs only carry javelins as a ranged weapon) and use my familiar and Shocking grasp to damage enemies on ground while I mostly dedicate to control-type spells.
As we reach the next orc village Druid gets inside a hut and receives a triple surprise attack from three orcs inside.
"You said you wanted to retire him" DM said when asked for an explanation.
Another thing he did was giving overpowered items to the wrong PCs thinking "this will improve your character" which is why he saw fit to give my wizard a magical shapechanging weapon (dude, I have no strength to write home about). Or giving something that looks like an important sidequest to a PC only to later take it away with no reasonable explanation, as when he gave Ninja a speaking shadow (his shadow became possessed by some spirit who started speaking to him to teach it stuff) only to have the shadow eaten by a monster next game session.
This kind of antics went on for about three more sessions, this guy still DMs from time to time but we have learnt that when he does we mostly try to laugh at his crazy attempts to murder the party, since he is clearly not changing his ways.
"You won't believe this, but you left him at 1 HP" is now the new "I'm the DM and I will BS this fight until I consider you've all suffered enough"