Seconding the annoyance at skill check crits/crit fails. I'm always reading stories from games where people roll a 20 on a skill and do the impossible, like achieving world peace on a crit Diplomacy check or unlocking doors that don't even have locks with crit Disable Device. It's so pervasive that I have to constantly remind my players to tell me their total roll when they get a 20 on a skill - if the DC is 35 and you roll a 20 with a +5 modifier, you're still going to fail! Conversely, if you roll a nat 1 with a +5, that DC 5 skill check is going to be impossible for you to fail at.
Name of PC: Romnir
Name of PC: Bertio
Story: I've got a few years of DM experience under my belt, but occasionally I still make mistakes. This was one of them. My party was on the verge of going into the Glassworks (they would have recieved Tsuto's letter to Ameiko the next morning), but a player was absent and I didn't want the remaining 3 to tackle it without her. So, I added in a side mission that I found in the Pathfinder Comic that involved goblins in Mosswood - I figured I could give them an exp boost and introduce them to Shalelu at the same time (who would be played by a friend of mine who stopped in to watch the game).
So my first mistake was setting up the encounter. Instead of facing the enemies (3 goblin rangers 1, 3 goblin rogues 1, a wolverine and a goblin cleric of lamashtu 6) in stages, I just dumped them all on the board and told the party to roll initiative, thus making a group of 3 level 1s and a level 6 NPC take on a CR 7 encounter. The party was easily overwhelmed by the goblins long before the goblin cleric joined the fight - mostly due to the goblin ranger's favored enemy hitting against both the half-humans.
My second mistake was not telling my friend, who was playing Shalelu for me, to focus her attention on the goblin cleric, who was the leader of that goblin tribe. I gave him no instructions, so he had her try to draw aggro from the goblins to get them to attack her instead of the PCs.
My third mistake was when the party started to think that the goblin cleric was a druid. I wanted to make him do something that would prove that he was a cleric, so I had him channel negative energy. 3d6 damage to everyone on the board, including two unconscious PCS. Even if I had rolled poorly they still would have died - and to make matters worse, I completely forgot about the Will save they were supposed to get to lessen the damage. So 2 PCs died, another was at her negative con, and Shalelu was brought to 4 HP.
Thankfully, my players forgave me, and actually enjoyed the encounter enough that when I offered to retcon the whole thing they decided to stick with the new characters they had made (with an exp bonus to make up for me killing them unfairly). I've learned my lesson about going off-book, and am so grateful that my players are so forgiving.
I'm two weeks into running Reign of Winter for a group of 5 and the lodge destroyed them.
Stats were rolled, and I encouraged them to be creative and take archetypes. They avoided the Snowman trap by going around it (walking backwards because they thought that's what "turn back" meant), they made all their reflex saves to not fall through the ice, and they saw the crossbow trap tripwire easily. However, during the earlier encounter with 3 raiders one of them got away, running back to the lodge to warn everyone, so the raiders in the lodge were prepared.
The party circled the lodge, peeking in windows and scoping it out. They saw all the healthy raiders gathering in the main hall, so they started planning their attack strategy. The rogue and the kineticist worked together to shoot a blast of fire into the room with the sick raiders, not killing any of them, but sending them running into the main hall. By this point, the inquisitor was getting impatient, so he declares "I am going to break down the door."
His strength check doesn't even come close. However, this is what finally starts combat - the 5 of them vs. 10 raiders inside (6 healthy, 4 sick). I have the raiders fight on defense, taking up positions near the doors and readying attacks for when the party rushes in. One raider goes for it and goes outside to fight them. He fights the inquisitor and the rogue (poor rolls on both sides means he's still standing after 2 rounds). The druid and the kineticist take up blasting positions near the stable (despite the druid not having any offensive spells aside from her domain power), and the monk circles around to try to drag Ten-Penny though the kitchen window.
After a 5 round stand off, the raiders make their move. 3 of them leave through the door near the well, sneak around the building and get the drop on the kineticist, knocking her down to half health with ranged attacks. The druid gets in front of her, intending to take the hits. She goes down to 0 and runs for shelter in the stable. The monk comes to help them, standing in front of them and taking a volley of arrows. The monk goes down.
The rogue, having finally gone into the lodge with the inquisitor to fight, sees them through the nearby window. "I want to dive through the window and stab the guy in the back," the rogue's player declares. "Okay, I need an acrobatics check for the jump, a strength check to break the window (you'll take damage), and an attack roll to hit," I reply.
15 for acrobatics, 18 for strength . . . 1 for the attack.
The rogue is now outside by himself, surrounded by 3 raiders. And one of them confirms a crit. So the rogue, the kineticist and the monk are all dead or dying in the snow. The inquisitor is doing pretty well by himself inside (he's the only one rolling well tonight), and finishes off the raiders. I decide to be merciful at this point and not have Rohkar join the fight - he'll still be there when they come back. One of the raiders outside goes looking for the druid in the barn, and gets stabbed by her readied action - which also puts her below 0 for taking an action while disabled. The inquisitor kills the rest of raiders, then finds his allies dead outside and finds the unconscious druid in the stable. Everyone else starts rolling up new characters while he goes and interrogates Ten-Penny, who is fully willing to cooperate after what she just saw. She picks the lock on the cellar door, they rescue Lady Argentea, and ride off back to Heldren, leaving the corpses of their allies behind.
Now, I'm considering what to do next. Part of me wants to be evil and have their former allies be raised as zombies along with the rest of the raiders, but I'm trying to stick to the campaign as written as much as possible and Rohkar just doesn't have the juice for that many zombies (his scroll of animate dead gets him 5, plus the 3 scrolls of lesser animate dead can get 3 more, and if I really wanted to, he could prepare lesser animate dead himself instead of all his 2nd level spells, but that's kinda pushing it). The replacement characters being considered are an azata-blooded aasimar gunslinger, a samsaran witch (white witch), and a human barbarian. I offered to let someone play as Ten-Penny, but nobody took me up on it.
I thought I'd have to boost some of the encounters to deal with 5 players, but after what happened, I'm glad I didn't.