The Lost City

The Lost City is the third chapter of the first book of the series, Threat From Beyond. It follows the Legends of Altmar on their journey through The Depths beneath the Spine of Altmar into the ancient city of Duuravhiin, undertaking a new dangerous quest.

Plot
The group ventures into the Depths below the Shrine of Exodus. There they find both oddities and dangers, and the lost secrets of an ancient civilization.

Synopsis
After taking shelter from the blizzard, and resting briefly in the strange ruins of the Shrine of Exodus, the party began exploring the waypoint, and found a loose floor that collapsed under Cal and Baravio. The cave-in revealed a deep tunnel that led far into the mountain which the party decided to follow. After sliding down into the newly revealed, passage, leaving Atlas above in the ruins above, the party decended into unknown Depths below.

After treking through the dank cavern that descended deep into the Spine of Altmar, the players fought off dangerous creatures before the cavern became deeper and damper. Strange fungi even Rikkert and Cal had never seen lined the walls and the air hung with a strange odor. Eventually the party discovered the cavern ended at a large fungal growth that blocked the way. Baravio blasted the blockage with a Firebolt spell, filling the air with spores.

The party entered into a beautiful cavern, with a shimmering lake and a small settlement built into the stone, where resided many people familiar and new. These included Alia's sister Leila, and her mentor Faust, as well as a handful of Falasan Rangers and members of Cal's clan. The touching reunions lasted a good while, and the party found everything they enjoyed in the small settlement. Only Rikkert was far enough back to avoid inhaling the spores Baravio had released, and as such, only he saw the truth.

The settlement was a figment of the party's shared imagination, a Lotus-Eater Machine designed to halt tresspassers by the Myconid civilization that resided in the caves beyond. Rikkert and company were apprehended by Myconid guards who took the party, most of whom were unconscious to the Fungal Caverns, where Rikkert was taken before Sovereign, the heart of the Myconid hive mind. Sovereign warned Rikkert of a great evil that destroyed the dwarves below and asked that the party ensure that the evil below never again be freed.

Upon waking, and hearing of this. The party was split about what to do. Cal, Baravio, and Niavara had had enough of exploring the mountain and were determined to continue on their mission to Strombran. Rikkert and Alia, both from a sense of duty, felt the need to investigate what sort of great evil plagued the Depths below. The party, unable to agree to a consensus split, and Rikkert and Alia headed down, while the others began their trek towards the surface. Not too long after, Cal began to feel bad about abandoning his comrades to whatever fate awaited them below. After a brief speech he convinced the others to turn back and return to the Depths. Meanwhile, Rikkert and Alia found themselves among hostile fungi, and nearly died in an ecounter with a purple spore colony, before being rescued by the rest of the party. Regrouped, the party continued their descent.

After destroying the monsters that nested in these caves (including a baby Rhemoraz) and braving the treacheries within, the group descended into a huge ravine nestled in which was the titular lost city of Duuravhiin. Once the mightiest city of the dwarves, after the Diaspora of the Dwarves, none had set foot in this ancient and empty place. Noticing an enormous sphere on the far side of the city and fighting off dangerous monsters who inhabited the seemingly destroyed part of the ruins, the party found a way inside the strange place. Inside, a walkway led up to a huge drop, and a central pillar that stood above it. When they approached, from below came a roar and the gargantuan form of the dragon Argorok.

Argorok informed the party of a great seal within the sphere that he watched over. The seal protects the world from a portal to a horrible dimension that was shut by the dwarves at great cost. Argorok watches over the seal and tells the player that the magic keeping the gate shut is weakening and that to restore its power, the party will need to bring four dwarven artifacts of immense power. After tasking them with this, the party left and ventured into the remaining part of the city. After exploring briefly, and looting an ancient dwarven vault, the group discovered a grand temple. Upon entering they saw on the upper floor a strange magical artifact, which they correctly presumed to be the Earth Stone.

After conquering the traps and trials of the Temple of the Earth Stone, the party faced the Guardian of the Earth Stone, a burrowing insectoid creature who shook the characters to their being. After defeating the Guardian, they retrieved the Earth Stone, and still unsure upon whether or not to trust Argorok, the returned to the surface and their quest to deliver the invader's remains to Fallharbour.

Upon returning the Shrine of Exodus, the party found a wounded Atlas with the remains of a giant Ice Spider that Atlas defeated when it descended upon him after the party's departure. Spending some time nursing Atlas to health, the party continued through the Northern Passage. After several more days of travelling through the blizzard, the party descended the mountain through an ice cave, reaching the bottom once more. After travelling through the snowy pass, they saw smoke in the distance through the ice and hail. As the group approached, they discovered the Iron Walls of Strombran.

Bestiary

 * Giant Ice Spider
 * Myconid
 * Myconid Sovereign
 * Violet Fungi
 * Hook Horror
 * Young Rhemoraz
 * Troglodyte
 * Black Dragon
 * Clay Golem
 * Umber Hulk

Trivia

 * First Appearances of: Sovereign, Argorok
 * This chapter's name is a reference to The Lost City one of the original modules for Advanced Dungeons and Dragons. 3 of the players have played this module, and the DM has run it on two occasions.
 * The boulder trap in the Temple of the Earth Stone is a reference to the iconic scene from Indiana Jones and the Raiders of the Lost Ark.
 * Both The Orrery and The Elemental Path were lifted and tweaked from encounters detailed in posts on Giant In The Playground and the D&D subreddit, respectively.