I definitely felt like this was back in the Shop Heroes setting. I want to write out a general summary to make sure I have everything correct so far.
An open letter was sent as a call for help, to seemingly anybody, to come to The Village. The players talked briefly on the boat trip to The Village, to each other, mentioning the letters. They all went to talk to the Mayor. The Mayor asked for the players to retrieve an item, of unknown nature, from the Sewers. The players accepted with great hesitation and suspicion. The Mayor requested they not draw attention their quest. The players asked around the Inn and The Village to gather information, but ultimately found nothing useful. The players performed at the Inn, making their presence memorable, then went to the Sewers that night undetected.
The village is patrolled by guards. The players waited until the Sewer entry was out of the guard's sight, and made a poor cover of their break-and-enter. The players were attacked by, and defeated, slime creatures. The players communicated with and followed rats to the Rat King, guarding the Shiny Gem. The players defeated the Rat King, took the Shiny Gem, and made their way back to the Sewer entrance. The way back was sealed off with no way to re-open the path.
Further in the Sewers, the players found a hideout and were ambushed by cultists. A cultist attempted to complete a ritual, but was interrupted. They defeated the cultists and stole some of their clothing. They found a map highlighting a path under the Town Hall and Thief's Guild through the Sewers. One of the players revealed that they have been through the Chaos Gate, demons do not like him, and that the cultists follow a known demon. The other players are mildly suspicious, but carry on. The players find an exit from the sewers and find a clearing in the morning. One player becomes an animal form to scout the area while the other players rest.
The scouting player finds nothing of interest and returns to the camp to find the Chaos Gate player missing, along with the Shiny Gem. The two remaining players have been drugged with a sedative. The 3 remaining players follow tracks through the forest to an attacked merchant carriage being picked at by a wolf and a dire wolf. In animal form, the player scouts closer to see anything of interest, but is frightened away by the wolves before anything can be seen. They follow the path further and come to a cross roads to a Wizard's Tower or where they see tracks leading. They follow the tracks and discover the cultist camp.
One player creates a distraction with the cultists guards, in disguise, while one other player searches for the abducted player. The abducted player is found in a caged cell, and the third player jumps into the fray as a shape-changed Dire Wolf to bring the guards away from the caged cell. The abducted player is freed from a prison cell, and joins the fight. All but one cultist is defeated. The final cultist says he has completed the first part of a ritual for a Demonic Invasion, explodes, and creates a shock-wave in the immediate area. The Shiny Gem does not glow as brightly after the ritual. A player is mortally injured, but is stabilized with a healing potion. The players find a few potions and a map of the area with the Mayor's name highlighted. Everything else seems destroyed from the shock-wave.
The players return to The Village. They overhear villagers talking about the break-in to the Sewers. The players suggest to the villagers it was likely a thief, and the villagers seem to agree. The players go to the Town Hall to report to the Mayor. The players explain what they encountered. The players intimidate the Mayor for a clearer explanation of why they were called to the Village. The Mayor explains that the Sewer encounter was noticed and he had to frame (another) known thief for breaking and entering. Due to this blunder, the Mayor requests the players perform another adventure before he divulges more information. He directs the players to the School of Magic for more information about the Shiny Gem and the Demonic Invasion.
The players encounter a teacher in the School of Magic. She doesn't directly know anything useful, but directs the players to Gloomy Manor. The previous owner of the Gloomy Manor was a collector of artifacts, and mysteriously disappeared. The players visit the apothecary to identify the potions from the Cultist Camp. The apothecary warns the shape-shifter player that the Mayor can't be trusted. The players return to the Inn. They have a musical performance duel. They win, and acquire a magically enchanted instrument. They retire to sleep.
Once again, the Chaos Gate player is missing. One player finds a note indicating that the Chaos Gate player is going to see someone, and if he doesn't return, he is likely dead. Players rush off in all directions, and eventually meet up at the Town Hall. After discussion, they find that someone planted the note, and none of them wrote it. The Chaos Gate player was investigating the Mayor's records and discovered fraudulent and pyramid-scheme-like means of borrowing and paying people in the city. The players decide that in light recent events, it is an opportune time to break into the Thief's Guild while many of Thief guild members are being rounded up due the the Sewer break-in. They find a Cloak of Sneaking.