Whenever I need an adventure for a single session, I think of my favorite entries in the One Page Dungeon Contest. One of the first entries I keep thinking of is The Ruination Of Tenamen by Waysoftheearth.
It’s an orc lair with a pit in front of a throne à la Jabba the Hutt with an owlbear instead of a rancor, a medusa living in secret passages, an underground river and other exits. Excellent!
I needed a lair for an ogre called Jugular who was the third ogre terrorizing an elf village. The party crept in through a back entrance, defeated the two orc patrols that tried to hold them off (wandering monsters). One of the orcs escaped and warned the others. The party crossed the river using rope and the levitation spell, ended up allying themselves with the orcs in the digs (killed the single male in the first dig, talked to the females with kids and demanded negotiations after discovering that they didn’t like their boss, either), sent Bolgug (who had organized a defense of the digger orcs) to fetch the prison keys (he wanted to rule the tribe as soon as the ogre was disposed of), but he acted suspiciously (I had decided) and was thrown to the owlbear. The party heard his screams and came to his rescue. Behind the pit stood the super ogre! I had given him 6+1 HD which ended up being 29 hit-points. The party had surprise on their side and fired arrows, then they gained initiative and fired more arrows, threw a spear and the ogre was down to one hit-point (I tell my players their enemy’s hit-points if they ask). The dwarf wanted to reach the ogre with his axe. I told the player that her dwarf could jump across the pit and hit the ogre in the face—but if she missed, she’d fall into the pit and take 2d6 damage. She went for it, made it, and slew the ogre!
The paladin wanted to jump down into the pit and help their orc-friend Bolgug. I told her that if she’d jump down she’d take 2d6 damage and she said she wanted to land on top of the owlbear. I said ok, if you hit the owlbear, you can add 2d6 to your damage. If you miss, you’ll take 2d6 damage. She had 9 hit-points left and went for it, and hit. The owlbear had 17 hit points and survived the hit. With the help of lady Luck she survived the counter-attack and in the next round, she slew the owlbear.
What a finale! We then rolled for treasure and got 1000 gp for the ogre and five jewels (30, 300, 600, 700, 1400)—in that order. It was awesome.
The players were a very good friend of mine and his three kids and the oldest girl’s boyfriend who had played for the very first time.