For a campaign that goes all the way to 20, you need a story arc that is on the level of "Save the World" so the powerful arch-fiends, liches and elder dragons you later will need to throw at the PCs have a reason to care. I found from earlier campaigns that a bait-and-switch in the middle of the campaign after the first campaign arc ends does not work as well.
The story goal of this campaign was literally "Save the World, and others too", although of course the PCs only realized this after they were about seven levels into it. It was build on the premise of Ptolus that the world was a prison the great old ones of Chaos, the Galchutt. (Much of this was taken from Monte Cook's Ptolus setting).
"Canon Hazen" is licensed under CC-BY 4.0.
In the campaign world cosmology, Praemal is the benevolent god that created the multiverse and the other gods, analogous to to Tolkiens Eru Illuvatar. Tharizdun, the cryptic god of the old first edition modules, is the lord of void that opposes creation. His goal is to undo it all. The Galchutt are his spawn and servants, just as the gods are the progeny of Praemal. Before time, the gods defeated Tharizdun and imprisoned him. To ensure that the Galchutt would not be able to free him, they likewise imprisoned the Galchutt, in the campaign world. The key to this prison is on the Vallis Moon. When the Galchutt first tried to break out, Praemal hid the Moon from the world, similar to what Eru did with Valinor.
Now the moon has re-appeared and the Night of Dissolution is nigh. Tharizdun sends dreams to his cult at the temple of All-Consumption, instructing them to excavate the old Temple of Elemental Evil and summon the Princes of Elemental Evil, to bind the moon with a four-fold chain. When the moon cannot again be hidden, the Galchutt can reach it, break out, and free him.
To put time pressure on the campaign, the cultists summon one more prince each full moon, and when all four are summoned, the final ritual is performed and the world will end. The PCs learn about the moon being chained and time running out in dreams their Moon Druid has.
The campaign consisted of the following adventures (recommended level ranges in parentheses). In the first section the players get dragged into a net of intrigue in the criminal underworld of Monmurg (my version of Ptolus, a mix of that city, Singapore and Melniboné), with little foreshadowing of the big storm that is about to brew.
- Ptolus (1-5, Monte Cook)
- The Murderer's Trail,
- Trouble with Goblins
- Smuggler's Daugther
- End of the Trail
- Shilukar's Lair
- Sewers and Ratman Nest
- Temple of the Rat God
- Temple of the Ebon Hand
- Mines of Madness (3, Scott Kurtz) This fun adventure had nothing to do with the main arc. As one PC was likely to die right at the start (and did), I played it as a dream-quest.
The characters by now were in the cross-hairs of several powerful crime organizations in the city, so they decided to go to the countryside and wait for things to tide over. Their friends in Castle Shard teleported them to the quaint Village of Hommlet, where they wanted to search for treasure in the ruins of the Old Temple of Elemental Evil.
- Return to the Temple of Elemental Evil (4-14, Monte Cook)
- Hommlet
- Moat House
- Ruined Temple
- Crater Ridge Mines: Water Temple
- Crater Ridge Mines: Earth Temple
- The Night of Dissolution took place, and changed the World and how magic worked - we switched from Pathfinder to D&D 5e. The back story was that the PCs did not manage to stop the cult from conducting the ritual of the Night, because they left Monmurg, and thereby gave free reign to the chaos cults to execute their plan. No the clock started ticking for summoning the Elemental Princes.
- Outer Fane
- The Sinister Bakery (5, self written based on the story of Krabat), a side adventure to resolve the backstory of one of their NPC henchmen
- GDQ1 Queen of Spiders (8-14, mostly Gary Gygax)
- Steading of the Hill Giant Chief
- Room 23 on the lower level leads off the map, so I had it lead to the underdark. Of course my players went down that way. I just riffed this during play with a portal of ominous warning (didn't stop the players, of course), chasms, gremlins, a huge cavern with a buried dead god crawling with hundreds of carrion crawlers as maggots feasting on his regenerating flesh (inspired by Death Frost Doom), a trapper, and a sepulchre with a mind flayer mummy that wore an iron mask; this was a nasty trap, if you donned the intelligent mask, it granted at-will detect thoughts and levitate, and secretly tried to dominate the wearer and use him to steer new potential slaves to a nearby a mind flayer city. The mask said it knew of a hidden cache of dwarven magic weapons. Lolth's avatar in drow form appeared anonymously to warn them, as she wanted them to continue against the giants and drow to put down Eclavdra. Greed won out in a party vote, and they forged ahead into mind flayer territory and lost three of the party in a narrow escape.
- They then went back up to the Yeomanry, as they hoped to learn how to buy freedom for their enslaved friends in nearby Sterich. My Yeomanry was a rotten place, modeled after Velen and the bog of crones from Witcher III. They made a deal with a a hag to deliver the head of the forst giant jarl in exchange for knowledge on how to free their friends. This is a good example how you can steer the PCs back to the main adventure path with a bit of improvisation, and without having to force them onto it -- normally they would have gone to the Frost Giant Rift from the Hill Giants directly.
- Glacial Rift of the Frost Giant Jarl
- They managed to find the back entrance with lots of magical scouting, and snuck in from there in a surgical strike to take out the Jarl and cut off his head, but did not manage avoiding the alarm being raised. In the flight from the enraged giant horde, a timely suggestion on the white dragon the giants had sent to intercept them at the back entrance saved their hides.
- Out of the Abyss: Mantol Derith
- Here they could deal with the mind flayers on neutral ground and ransom their friends (thankfully they were rich from plundering the Hill Giant treasury). They also hired a renegade drow mage to help them find their way to the Vault of the Drow. He of course would later try to betray them to get back into the good books of his house.
- Hall fo the Fire Giant King
- Again, they avoided most of the encounters by scouting with 5e's advanced magical powers (summoned earth elementals, druid turning into an earth elemental) then found the entrance to the underdark underneath the Giant Hall, and went there directly.
- Warrens of the Troglodytes
- In the underdark, they again used magic and invsibility to avoid confrontation where possible, for example, sealing themselves in side caves with stoneshape to rest. There was a memorable random encounter with a lich that in exchange for payment in magic items and arcane knoweldge, agreed to not only spare their lives (well, they had to raise one of their number from the dead after it used power word kill to clarify it was not messing around), and traveled with them as a companion. This was quite helpful, as it could get rid of evidence by shoving the drow corpses into a demiplane.
- Shrine of the Kua-Toa
- Again the players sidestepped the entire city. They had an NPC Drow Mage in tow, too, who helped them navigate the alien environment of the underdark but of course was planing to betray them to his house, once they go to the Vault of the Drow.
- Vault of the Drow
- So he did. They however struck a deal with Eclavdra: they would assassinate the high priestess of Lloth, so Eclavdra could convert back and become the new High Priestess and unite the warring houses under her power. Loth was down with this idea.
- The demonweb pits
- They met Lloth again, who had learned about Tharizdun and his plans through her investigations of the Elder Elemental Eye. She had just wanted to make sure they were strong enough to stand a chance against the elemental princes, gave them gifts and freed Hazen. (This "test if you are worthy" angle is lame, I know).
- Temple of Elemental Evil (1-8, Gary Gygax with Frank Mentzer) Elemental Nodes
- By now three princes were summoned. They killed two, then the forces of the temple pulled back into the inner sanctuary of the old temple with the remaining prince of Air.
- Return to the Temple of Elemental Evil. Epic battle against all the remaining cult leaders in the inner sanctuary of the old temple. They managed to destroy the altar that was required for the ritual, so the cult was held off for least a year while they built a new one. In that time they wanted to find a way to Praemal via the Jewels of Parnaith, and petition with him. But how to get to the Jewels? The most likely place to learn this was in Jabel Shammar, so the question was how to get in there?
The plan for the campaign (level 15 to 20) was as follows
- Ptolus.
- Prison (entry to the crypt of the "demon-lich"), with bronze dragon guardian, and undead guards -- the backstory of one of the PCs from level 1 had the maps to find this place, in a chest of adventuring heirlooms he inherited.
- Self written upper level of the crypt.
- Tomb of Horrors (10-14, Gary Gygax). Learn that there is a portal to Jabel Shammar in Goth Gulgamel. No need to fight Acerak, I put his library with the clues in an earlier room.
- Ptolus
- Goth Gulgamel (13-14)
- Jabel Shammar (19-20) learn how to access the Jewels of Parnaith
- Homebrew Finale (the Jewels are barely described in Ptolus, I planned each jewel had different laws of reality, and was its own little adventure, similar to the way it is towards the end of Desert of Desolation, to make this all a bit of a dream-like quest, where the PCs powers would wildly fluctuate from Jewel to Jewel.)
However, the entire party was annihilated at the Green Devil Face in Tomb of Horrors, so other heroes will have to step up and save the world. In another campaign. Maybe if I had not put a Green Devil Face that was a teleporter to a location with a dangerous fight at the other end into my prequel level to the tomb, they would not all have lined up and jumped in...