The "Granny Incident"

The Slaughter of Mt. Silena Aethel
The Slaughter of Mt. Silena Aethel - or alternatively "the granny incident", as Vestkanten Crew reffered to it as - is the event of which the entirity of the isolationistic, elven town located on top of the mountain in Brienn: Mt. Silena Aethel, was slaughtered by devils. Summoned by the night hag Granny Gravenight.

An Herbalist's Escort Mission
On the second day of the Festival of Strong Walls and Strong Friends, Vestkanten Crew was greeted by a young woman: an herbalist in need of bodyguards, for her trip up Mt. Silena Aethel for important alchemical ingredients. Looking for good coin, and other opportunities for an adventure, Vestkanten Crew accepted. The trip lasted three days, with barely any incident. The only noteworthy thing that happened, before Vestkanten Crew entered the town, was that when they killed a goat: it disappeared in what was explained as "demonic smoke". Around which point the young herbalist had gone missing.

After arriving in the town, it didn't take long for Vestkanten Crew to get into trouble, and were forced to flee into the nearby mines. In which, after a few hours of navigating the tunnels, they found a underground, dwarven mining colony. Hiding from the surface elves. After a day of catching their breaths among the kind, and rowdy dwarves. Vestkanten Crew emerged to find the elven town in ruins; blood, corpses and rubble all that was left. Save for one survivor, whom died in Erevan's arms during interrogation. Yet their answers came quickly, as the final devil was being summoned by Granny Gravenight.

Archon Jon, and The Thirteen of the Inquisition
In the town square, Vestkanten Crew finally found the young herbalist, turning into her true form: the night hag Granny Gravenight. Summoning the Archon of fire and domination, Jon. With the help of the timely arrived Thirteen Inquisitor, Vestkanten Crew fought and defeated Jon, sending him, and Granny Gravenight back into the portal. To whatever hellscape they were returned to.

Trivia

 * Tommy started out as the DM for the introduction of this arch of the campaign, before Ulrik took over, as it was his turn to be the group's DM.
 * The elf that died during Erevan's interrogation, died due to a heart attack, because Erevan's player Tommy rolled a natural 20 on his Intimidation check.
 * Jon was first introduced as a generic horned devil.
 * Jon was never planned, not even his name was. Ulrik, at the time, simply needed a big bad boss for Vestkanten Crew to fight (and a name for him).