Half a year after the Siege of the Winter King's Palace, the PCs come to meet the return of Jarl Olaf Henrikson's ship. But those who depart bear injuries and looks of terror and defeat. One of the sailors, a man by the name of Hallbjorn, greets the PCs and tells his tale.
The jarl set sail for new lands in the Far North. When they camped out at the nearest shore, a war party of Ulnat lead by an otherworldly figure was among them. Jarl Henrikson died in the battle; pursuing their attackers for vengeance, Hallbjorn's team discovered a strange name from some Ulnat who also suffered their depravities: Althunak. Sadly, although they tried to fight, the cult of the demon-god was too great, and there must be survivors to spread word back in Silvermeade Hall.
Inga, the next inheritor in line, gave the party her blessings to go and avenge her father's death. Sailing upon her old father's ship with Hallbjorn as navigator, the PCs set sail for the Far North.
The journey was cold and uncomfortable, yet full of adventure: whale hunting, finding a wrecked Jomsviking ship, and two storms (one of which was accompanied by giant enemy crabs!), the PCs lost Hallbjorn during the torrential weather and Vigbjorn was appointed the new ship's leader.
Two days afterwards, the PCs found a lone Ulnat woman adrift at sea by the name of Aluki. Knowing only her native tongue, Syrasi acted as translator, where they discovered their worst fears: the Cult of Althunak is indeed growing in number.
Directing them to her home village of Larquiv, the PCs met with one of their elders and learned that the tribe has dominion over a meteorite-turned-tomb known as Heroes' Rock. With its ample supply of cold iron, it's been coveted by other tribes, as well as containing weapons capable of cutting through demonflesh. Also the Cult of Althunak in the region's being led by an Ulnat man by the name of Elvanti, who departed his tribe out of spurned love and returned south with abyssal minions and unholy powers. Ever since he's been a scourge in the Far North for 10 years.
And so the PCs sailed to Heroes' Rock, intent on proving their worth to gain access to the sacred weapons therein to use against the Cult. The trials within are physical as well as mental, for after fighting a corpse-stitched troll invested with spiders the PCs met face to face with the specters of the Ulnat heroes of old. Askeladden proved their worth by retelling the party's deeds of valor, and as such were lent the magical items necessary to fight the Children of Althunak.
After departing, the PCs decided to go about Ulnataland, liberating villages from the cult's clutches. The first village of Gualivik was right near Heroes' Rock, where cultists were loading up the enslaved tribespeoples' weapons into a wagon and burning the rest. After using a magical distraction, Vigbjorn charged forth in a surprise attack, slaying their leader with one blow. Slaying several more, the cultists were routed and the PCs gained the loyalty of 12 Ulnat warriors in future assaults.
The PCs' next destination was the last camp of the Long Serpent, bearing cairns containing the bodies of Jarl Henrikson and the comrades who fought by his side. Sailing past a razed village, the party found a mysteriously empty igloo village awash with demonic dogs lead by an Althunak shaman. The cry of a nearby baby motivated the heroes to save it before the monsters could get a hold. It was a hard battle, but once again the PCs were victorious.
The party set out to liberate another village, finding a group of elders frozen by Elvanti's curse. Using the fireball wand from Heroes' Rock, Syrasi destroyed the abyssal ice, prompting the wrath of the local cultist and his two demonic allies. The battle was won, and 10 more Ulnaut from the village enlisted their aid. The next village was relocated, tracks in the snow leading west to the temple being built in progress in the middle of a quarry.
Aluki and 39 Ulnat warriors were there to help the PCs, who then formulated a plan. The idea was that Syrasi and Amund, aided by magical flight, would take Askeladden and Vigbjorn down, raining death on the cultists' tents while the Ulnat went down the gravel slope to the northeast to free the slaves.
The plan was quick and precise, the PCs firing arrows and hurling rocks as they landed, with Vigbjorn killing a shaman before he could complete a summons while Syrasi torched the remainders with a fireball. The Ulnat were having about as much success, and quickly the bulk of the cultists' forces were pushed to the large demonic statue of Althunak (a beastly visage of a many-fanged humanoid with an orb in one hand and a sickle in the other). There the two forces encountered the red-robed High Priest, flanked by two more serpentine demons and loyal bodyguards standing atop the stone steps.
Dire Bear by Just Jingles of Deviantart
What at first seemed like an ordinary practitioner of the dark arts turned out to be a werebear, as he changed form and gave Askeladden and Vigbjorn a run for their money. Thanks to some timely hexes from Syrasi and an aerial boulder assault from Amund, the party chipped away, cursed, blinded, and finally killed the high priest, causing the cult's forces to scatter. Feeling emboldened, the slaves took up the arms of the fallen and killed the remaining cultists with the warriors. But the final victory came when the statue of Althunak was brought crashing down. The demon-god's influence would not take root in Ulnataland if they had anything to say about it!
Enriched with loot and a sacred staff from Aluki's elders, the party decided to stay in the region for a bit, at least until the next adventure...
GM's Notes: The Jomsvikings ordinarily do not make an appearance proper until Raven Banners Over Gatland. But they are one of the few recurring villains in Northlands, and they do have a reputation of utterly mercenary and ruthless folks, so I wanted to scatter things like that throughout the campaign as a taste of things to come.
I read that some real-world Inuit tribes made use of meteorite iron to forge metal harpoon tips and tools. And since cold iron is a classic weakness to many demons, I figured that the Cult of Althunak would have a vested interest in trying to subjugate or destroy Laquirv. Hero's Rock was just an ordinary tomb in the original module, but I decided to turn it into a repurposed meteorite containing cold iron, with the legendary weapons gaining said properties too.
The Ulnat scout in the lone kayak in the original adventure is a man by the name of Yilithi. I felt that so far the Northlands had a significant proportion of male NPCs in major roles, so I threw in a woman who would also act as a sort of guide to the Far North to even things up a bit. Given that the players liked her enough to have her on as a Leadership cohort later on, I think I made the right decision.
The Second Temple of Ice and Stone was originally high up on a plateau. I misinterpreted the incline lines on the map to be going down instead of up, but by that point the players were already formulating plans based on this.
There were more demonic monsters than would ordinarily be in the original adventure path. I wanted to add some variety in the encounters beyond cultists and cult shamans with identical stat blocks, and wanted to play up the usefulness of the cold iron weapons.
The use of a fly hex and the party riding on a rock-throwing giant as they descend is one of the things I love about Pathfinder. It adds in great and unorthodox plans like that while still having a variety of enough options that things won't get old. Granted, actual long-term flight is well below the group's level at this point in the campaign.