Investigate the Mage's Tower's construction site

After realizing they would no longer be able to accept work out of Greensward Libertas Dacia moves to the big city, Rubi'Sarha. This has several motivations; first they can get paid more, second they are closer to the Kilimenga Expanse, the last known whereabouts of Oswulf Plümmer, and lastly close by to Vanadis Peak peak, a key location for Ostreliea.
After emerging from the teleport circle in Rubi'Sarha they wander to find the 1st Adventurer's Lodge Hall. The inside is much different than the close familial feel at the Brazen Hearth, vendors have set up shop right at the Bay Doors on the near side. The space seems almost cavernous and unwelcoming until they meet Richard Humbleborn working behind the counter. His warm demeanor and mindfulness puts them at ease.
He recognizes them from Maeve's boasts and helps them find a job appropriate for their level. A mage had recently discovered a convergence of ley lines just north of Mountvine, and commissioned a tower be built there for observation and research. However the members of the craftsman's guild sent to work the site, broke into an underground structure. Several went to investigate but none made it out. The foreman decided to pack the crew up and head home before more of his own decided to try their luck spelunking the ruins.
The party is to investigate what caused the disappearances, ascertain whether it is a safe working environment, recover what they can of the missing crew, 7 in total. The gold bounty on return is 1600 GP.
They quickly provision up and begin their voyage across the sands. The first day of travel is quiet. on the second though they meet a man with a dire need for water. He tells them that they had set up camp, possibly had to much to drink and after a large storm were all scattered. With the water he heads south to Mountvine. The party goes to investigate, and find several bodies eviscerated torn by claws so sharp the cuts looked as if they were made by a blade. Upon further investigation they find a stone circle engraved in a language they do not know. Araz attempts to handle it but senses some malevolent spirit attempt to take hold of him, he drops it before it's too late. The third day goes well enough to make up for their lost time the day before.
Upon arriving at the site they see a large tent setup and a man sleeping soundly within. Pious tries to enter but is stopped by some sort of barrier. They wake the man inside. Phineas claims to be the mage who requisitioned this tower and that he's put off by the craftsman's guild failure to complete the task despite their losses. He's short with the party and expects them to do their job quickly so his tower can finished sooner rather than later. Begrudgingly they proceed under ground.
Mess sends out his undead familiars first, he sees that the structure below is probably of Dwarven construction. He guides them even further until there is a fork in the road one through a solid, well built dwarven door, the other down a set of stairs. He pushes on down the stairs and loses sight from the rat. Confused he calls them back. The rat does so with difficulty and never recovers it's sight, so Mess squishes it.
With the way ahead empty they proceed onward, arriving at the dwarven door without trouble. There seems to be some power drawing them down and agitating several members of the party. But against this impulse they proceed through the door of dwarven construction. Inside they find themselves in a receiving room of some kind. Further in they hear resonant crashes which seem like some sort of fight. Mess is able to read some of the dwarvish and it is indeed a reception area for some kind a research facility, or at least that's what a ledger would suggest. Just ahead they find a hallway conatining some sleeping quarters, and the sounds are nearer almost as if it's upon them. Pious sneaks forward looking into the next large room, four elementals are fighting and with the damage to the surrounding area it seems like it's been that way for a long time.
Instead of immediately aggressing on the elementals they inspect the other rooms. Pious finds that one of the tables is marked by the force of someone's hand while writing a letter. "Cranock has gone mad, he's killed three and locked himself into the sanctuary."