Well, here we go, yet another thread about this little piece of world building.

Under the Tel Vos jail, we find Tel Vos Dungeon and a set of 5 notes from Foreman Beram who was in charge of building the dungeons, and getting pretty upset about the fact that despite the fact the Telvanni mages personally gave him the plans for the dungeon, his work is constantly being ruined by the roots of the Telvanni mushroom tower.

While working on the dungeon a rock collapses killing two of the 5 workers and trapping the remaining 3, with no way back up. Due to lack of food, rising heat and constant shifting of the roots, they choose to go further in to look for another exit. One more is confirmed dead found as a head in a pool of blood, killed by an unknown attacker. The last note is found next to the pool of lava and a flame atronach (assuming it hasn't walked into the lava before the player sees it) it only states "He is here!"

There are no bodies found inside the dungeon - it is however infested with increasingly aggressive "rats and bugs" so they could have just eaten the bodies. There actually was another exit, it even has a pretty little entrance built around it. However the whole scenario is still puzzling.

Now, if this was any other Telvanni lord, this story would be very simple. The Telvanni just killed them. The note "he is here" would even imply that, as the person writing clearly knew who "he" is and the level designer assumed it will also be clear to the player. Realistically, this is probably a disconnect between the person doing the level design and a person writing the NPC's above - but master Aryon doesn't come across as a person who would just kill people working for him without a good reason. He is trying to establish relationship with the nearby Ashlander tribes, he has argonian and khajit guards in his tower, the people of Vos consider him a great benefactor that drastically improved the lives of the population. (EDIT: Even Berwen in Tel Mora, when talking about the Corprus Stalker, mentions that normally Master Aryon would take care of it, despite her shop being under the jurisdiction of Mistress Dratha, meaning that he has also been helping the people in the neighbouring settlement)

I would still like to have a headcanon that does make it all fit together rather than miscommunication between developers. And the questions are many - Did Foreman Beram and his last unaccounted for crew member survive? Did they die to the atronach or did they find the exit then understandably ran away? Who is HE? Did Aryon really personally kill them, were they kidnapped, is the khajit in the jail the last remaining member of the dungeon crew (EDIT : No he is not, we actually do know the names of the last 3, I for some reason thought we don't the name of one of them)

The one interesting thing about this topic that I haven't seen brought up before is that Aryon is fascinated with Dwemer artifacts, he has his own little museum that you can visit and look at his possessions, and inside the dungeon you will find Dwemer Limeware and some coins, so this could imply that building of the dungeon was a cover up for digging a tunnel to access Dwemer treasures under Vos. The tree roots could have even been actively digging through the ground in search for the Dwemer ruins, that while not accessible in game - must be very close to the Tel Vos tunnels, close enough that some items bled into the caves. It is possible that Aryon wanted to make sure they will stay quiet about the found items, or the last note is really misleading and Aryon was there, but he simply helped the remaining two get out of the cave, which would be pretty funny