Stephen King's The Dark Tower series was a big part of my inspiration.
The players rolled up eighth level characters, as I'd intended this as a one shot. We had an enchanter Wizard, a Paladin with a holy six shooter, and a Ranger with a Camaro, gloves of infinite machetes that he threw, and a puma animal companion. The Ranger picked up the other two as they were hitchiking along the side of the road, and then they all sat in awkward silence as they drove on. Someone turned on the radio, and, as they were driving through Tex Arcana territory, I had them roll on my radio encounters table*. They rolled a sleep spell, all made their saves, and drove on. About midafternoon, I had the car blow a tire as they were passing an exit, and they pulled into a little mining town. They got stuck for two days while a part came in for some bit of the car that was damaged (I know nothing about auto mechanics), and went to a local bar where they heard that the town had several mysterious deaths. The Paladin detected evil and found out that there was evil coming from the abandoned slaughterhouse on the edge of town.
They decided to check it out, and started searching around. In a back room, they found the bodies of a few dead people drained of blood and rotting, then, when they ventured to the main slaughterhouse floor, they were attacked by three Urdefhan. All three hit the Wizard with Rays of Enfeeblement, dropping him to 1 STR and on the floor. They'd also hit the Ranger, and he was mostly useless. The Paladin started smiting with his gun and blew one away. The Wizard cast Murderous Command and the second Urdefhan killed the third, and a Scorching Ray and another bullet killed the second. They thought they were badass, got burgers at the local diner, and then went back to the off highway motel for some shuteye.
Urdefhan. They're demons, not undead, oddly enough.
The Paladin was woken up by Jesus in a dream (yes, Paladin of Jesus), and looked out his window to see a looming, shadowy figure radiating evil on the edge of the motel parking lot. He woke his compatriots up, but the figure disappeared while he pounded on the wall. The next morning, the sherrif was found in his office crucified on the wall, the diner owner was dead, and bits of the lady running the motel were all over the parking lot and a trail of bloody footprints and dead insects leading out of town. Feeling somehow responsible, they followed, ready to kill stuff.
They came across an abandoned mine where the footprints led, and started dungeon delving. In the first few rooms, they came across a poltergeist, fought it, and survived. There was a caved in section of tunnel with a small gap they had to worm through, and there was a needle with poison on it. The Wizard made his save and nullified the poison, the Paladin did too, but the Ranger and Puma took Constitution damage. After a few more tunnels and crossing a chasm, they came to a room with a pool of water. The dead started rising from the water, and they found themselves with their backs to a chasm facing down wave after wave of Juju Zombies. Luckily, I forgot the sneak attack on the stats from Bestiary 2 or everyone would have died. Luckily, one of the characters saw a wooden grate on the far side of the room that covered a tunnel. The Ranger broke the grate while the others held off the zombies, and the zombies seemed reticent to go near the grate which nobody picked up on.
Juju zombie! Surprisingly hard to deal with.
The Paladin detected evil, found it emanating from behind a door, and they deliberated. The Wizard opened the door. This was a bad idea. He got engulfed by the Worm that Walks Antipaladin that was waiting on the other side and almost died. The Antipaladin then shut the door. While the wizard was proper fucked on the other side of the door and went unconscious in a swarm of insects, the Ranger thumbed his bum as both he and his Puma were low on hit points and options after the Con damage from the poison and the zombies. The Paladin took manners in his own hands, opened the door, channeled his Lay on Hands into his gun because of some feat, declared a smite, and then rolled a crit. Now, the Worm that Walks didn't have all that amazingly many hit points (around 60-70, I think), and the smite bypassed its considerable damage reduction and swarm traits, and one shotted the boss I'd spent about two hours statting out before he got a real turn.
He looked something like this.
And that was all she wrote. That session turned into a mini campaign, and the Worm That Walks was retconned to be an avatar of Envy, one of the Seven Deadly Sins. They dealt with Greed and had a run in with Chastity (one of the Seven Virtues) and War and Plague of the Four Horsemen before the game fell apart.
-* The Tex Arcana, as necromancers, like dead stuff. They have radio towers in the area that broadcast spells through radio stations so that when people tune through radio stations, they can get hit with spells, crash, and die and give the Tex Arcana more dead minions. I couldn't find the table I made for the adventure (actually, I have a notebook with NPC names and everything that I couldn't find and might have accidentally thrown away which is sad), but I remember it was a D12, because I like finding uses for D12s because they're criminally underused. In the spirit of completion, here's a table. Spell DCs were 16 or 17 so they were liable to work if people rolled low, but weren't liable to cause a TPK, because I'm a relatively kind GM.
7-Shatter (on vehicle)
8-Cause Serious Wounds
12-Wall of Stone (in front of vehicle)