The Underdark is not a hospitable place. Although various races such as Drow, Dwarves, and Svirfneblin have all found their way to inhabit these dark, huge, compounds of caves, the Underdark is a vast land of danger. There is no sunlight nor fresh air to make any flowers bloom. There are no safe spots to sleep or rest either, unless it is a city. And even cities are dangerous as well, for drow and duergar are not the kindest of races to outsiders.
One of the facts about the Underdark that causes the most skillful and experienced adventurers tremble is the fear of the unknown. Many uncharted locations in these deep, wicked caves are intimidating to any would-be explorer. Demons and evil creatures dwell in the depths of the Underdark lurking, stalking, ready to creep up on anyone foolish enough to wander through their domains.
Such is the case of the Planetarium, the forgotten proof of a twisted, crazy mind. Hidden in the depths of the Underdark, this combination of magic and architecture holds a valuable treasure. Its creator was a Drow who became obsessed with mazes and torture. Azarin was a necromancer sorcerer who spent his life developing this masterpiece. He created an enormous device to torture people while entertaining himself. He liked the idea of creating a sort of test, a trial. He studied the planes’ architecture, and came up with the Planetarium. A combination of culture, art, cruelty, and evil.
Each of the four rooms in the Planetarium represent a different plane. The first room is the smallest, because of the corridor. The Astral Sea is the central hub that connects to other planes and it is depicted in the first section of the carousel. The walls of the entrance corridor depict alien scenes of planeswalking ships traversing the great Astral Sea. This first section of the pseudo-maze has an elvish inscription on the wall. It says: “In order to survive and acquire great treasure, you must persevere and reach the end of this trial”.
The second room is a combination of the four main elements: fire, water, air, and. Azarin thought the elements were the balancing forces of the world and the material plane itself.
The third and fourth sections of Azarin’s device give the spotlight to the Shadowfell realm and the Feywild respectively. It is common knowledge to any planes-savvy scholar that these are the two planes that coexist in time and space with the Material Plane. Azarin deemed his masterpiece finished once his Astral Sea room had access to all four elements, the plane of shadows, and his home plane, the Feywild. As a drow, the Feywild was the plane he felt more in connection with. He was proud of his fey ancestry. He was pleased with the final result.
When Azarin lived, he hid traps close to his lair to snare passers-by and adventurers. He did not care if they were humans, dwarves, or even other drow. He would paralyze them with poison and then take the prisoners to the Planetarium. After the main hallway, the entrance to the carousel-like structure is behind a stone prism that functions with magic. The prism stone slides aside to reveal a small corridor into the structure. From there, magic or manual labor can be used to rotate the central room to reach the other rooms. This mobile central section of the planetarium is the only means to access the rest of the rooms. This is where Azarin would place his victims and start his sick entertainment.
After placing his victims behind the prism stone, they had no other option but to traverse the circular structure. The prism stone cannot be activated from inside the structure. If his victims did not find a means to move the platform, he did it for them. Once his prisoners reached the second block of the Planetarium the real fun began for Azarin.
Azarin had a friend in the library where he used to live, his name was Yazin. Azarin told him about his project many times, trying to convince him of joining him. Yazin liked Azarin as a friend but he considered his ideals were not practical. Plus, he did not want to invest any time or money in this “Planetarium”. Azarin did not find the help he was looking for and abandoned his friend. However, Yazin kept many of the drafts his former necromancer friend had made. The other librarians knew about his intellect and were well aware of the books and readings he fancied. They also read on Azarin’s notes about the prize at the end of the maze, reserved for those worthy of finishing his trials. When the wicked necromancer left his birthplace to continue his life project, Yazin and the other librarians told everyone about it. It was not very hard to interpret the drawings and notes he had left behind. The word spread in limited circles about the great treasure he hid.
After he passed away, cities in the Underdark kept telling Azarin’s story generation from generation. It has been about two centuries since Azarin died but his name is still somewhat popular in the Underdark. Tales of great treasures and secrets are part of the common gossip. Azarin was, after all, a very skilled sorcerer and necromancer. The Planetarium could be the hiding place of great knowledge and wealth, but only the most courageous, wise, and strong are capable of crossing the representation of the Astral Sea and traverse the rest of the planes featured in the Planterium.
1 Entrance and Main Hall
Azarin loved astrology, and he decorated the walls of this corridor with the stars of the Feywild night sky. Astrology connoisseurs recognize constellations with ease. The stars cover all the walls of this hallway.
The prism stone entrance to the first section of the Planetarium (Area 1) needs magic energy to activate. Any spellcaster can spend a second level spell slot to power it. Adventurers trying to move it by force need to succeed in a DC 22 Strength (Athletics) check to move it aside. Either way, once characters have crossed the threshold and enter the Astral Plane section, the prism returns to its original position and blocks the way out. At this point, it becomes impossible to move it unless the structure spins four times, thus finishing a whole turn.
2 Main Corridor, Astral Sea
The walls of this section depict the waves of the Astral Sea. One Gythyanki ship sails proudly on the right wall. On the left, there is a plate of metal with an inscription. It explains that the journey has to be completed to get out. The three other planes must be visited to deactivate the prism blockage.
3 Plane of the Elements
This room has beautiful decoration on its walls. Starting from left to right, snow-white winds move swiftly to the right, transforming little by little into red fiery flames. This red-blood fire is accompanied by yellow and orange touches that make it look very real. Then the fire starts turning white until it becomes a pale blue, which in place turns sea blue. The massive waves crash to give place to a brown sandy shore. The shore grows and turns into hard stone. It is the work of a master painter. Elvish runes on the wall say: “The balance of the elements is key to attain wisdom”. Hundreds of bones and skeleton skulls lay on the floor. They belong to the victims Azarin trapped and did not make it past the first stage of the evil test. Many of them look charred and burnt. Half the room is considered difficult terrain due to the number of bones scattered on the floor.
Inside this room, there is an elemental creature waiting. It is an elemental construct Azarin created. The creature respects the order of the paintings on the wall. At first, it looks, behaves, and moves as an air elemental. When its hit points are reduced to 75% of its total, it turns into a fire elemental. It shifts to a water elemental and finally to an earth elemental when its hit points are reduced to 50% and 25%, respectively. When the creature dies, the magic stone that held the monster together falls to the ground. This is an ioun stone (DM’s choice).
After defeating the elemental, the structure moves on its own. The central section rotates and moves to Area 4.
4 Shadowfell Plane
Once the massive wheel mechanism moves to this side of the Planetarium, a reeking smell fills the place. The walls of this section feature a scene of human cities and settlements swallowed in darkness. A black sun spreads its darkness over the grayish and somber locations. This represents the impurity of the material plane. The Shadowfell is a reflection of all the evil that hides there. Elvish runes on the wall say: “All that is good holds evil inside. The opposite is true too, that is the right order of things”.
The room is littered with what appear to be rotting corpses. Some of them get up and attack the adventurers. There are five zombies, five skeletons, two ghouls, and one ogre zombie. A passive Perception score of 18 or higher or a successful DC 18 Wisdom (Perception) check reveals a chest camouflaged against the wall. It has the same paint as the walls so it is almost unnoticeable. The chest contains a cloak of protection +1, a +1 elven longsword, a +1 elven longbow, a bandolier with six healing potions, five cleric spell scrolls (DM’s choice) and a spellbook with 10 spells (DM’s choice). The treasure appears to be a way to prepare for the last section of the Planetarium. The moment the undead are defeated, the structure spins by itself once more, taking any survivors to the last part of the Planetarium.
Sophisticated and fancy paintings of natural landscapes, lakes, trees, and beautiful creatures fill the walls of this last section of the Planetarium. One last elvish group of runes on the wall read0: “Only when you understand nature is not guilty of your sins, will you be completely free”. Each of the three corners of the room has a dark-blue circle on the floor. The room has an ornate chest laying in the middle of the room. This chest contains Azarin’s most valuable treasure, however, it is not locked.
This room is a riddle in itself. When the chest is opened, three fey spirits appear in the three circles on the floor. These spirits take the shape of any CR 1 or CR 2 animal beasts featured in the MM. The beasts move towards the character who opened the chest in a menacing way. They approach slowly until they are adjacent to the offending visitor. Any attack or hostile movement against the spirits causes them to retaliate and attack. Roll initiative! If this happens, the chest closes shut again, until violence stops.
If the spirits are dealt with, characters can try opening the chest again. It is not locked. However, the moment they do so, three more spirits appear. They behave the same way as the previous ones. The same process repeats over and over until adventurers understand the spirits are not hostile. If the spirits are ignored as they approach menacingly for a minute, they return to their summoning circles and disappear.
The chest can be emptied then. Once the chest is empty, the Planetarium turns one last time, allowing any visitors to return to the Astral Sea hallway. The prismstone at the entrance moves aside, the prisoners are free to go.
Planetarium. The Planetarium is a huge mechanism. It makes a loud sound when it turns. The stone against the stone produces a harsh low vibrating sound while it turns. The whole structure works with magic as long as the conditions stated in each of its sections are met.
Decoration. The decoration on each of the rooms do not show any signs of battle. Magic coating has kept the art intact.
Azarin. Azarin was obsessed with his game and did not care about killing innocent people. But in the end, he cared very much for the planes and the balance of the world. The riddle in the last room of the Planetarium reveals that deep inside, he respected the fey spirits. No one ever got to finish his test while he lived. He wanted to make people understand the importance of the Feywild, and how it contrasts with the other planes.
Entrance Prism. This massive sliding structure is made of dark-green crystal. It responds to magic as long as there are no people inside the Planetarium, otherwise, it is unmovable.
DM’s Info. Area 5 does not describe the treasure. It is left to the DM’s discretion what to use. Besides gold or any monetary reward, it is recommended to feature a powerful magic item or an object the PC’s have been looking for. The reward can also be information about the party’s mission, or intel regarding a long-term quest.