This homemade, three-session adventure sees 4 players at Level 18 ascending through increasingly difficult and chaotic challenge rooms on their way to the top of an Arch Lich's private sanctum. This is designed to be run in a single adventuring day (no long rests), and with appropriately high level gear and equipment. It also assumes some level of veteran status in your players; while it can be run with new players, effective use of high level abilities and action economy is necessary to survive the tower, so I recommend running this adventure with no more than two people who are new to D&D.
Anything core dnd 5e is allowed (published sourcebooks, main books and supplements, but no homebrew for balance).
The main thing to keep in mind for character building is that this is a lich's tower (plenty of undead) and there will be a significant combat and puzzle solving challenge.
For Items: Each player has 35,000 Gold to spend on magic items and equipment (140k for the whole party). You may use this budget to buy anything from the following list of magic items, with the caveat that it cannot be a Legendary item. If any of you finish and have excess gold you can pool it to buy something better for someone else in the party, or extra potions. This list is also available in PDF form if you google "Sand Magic Item Prices." The items on this list are from the core content; if players want some other item from more recent sourcebooks, use your discretion to give it a fair price using this list as a reference for comparable item costs.
Basic starting equipment, such as non-magical armor and weapons and rope, is free (except for half-plate or full plate armor, those cost 750 and 1500 gold respectively.) Magic armor costs gold per the above list.
I limit each player to purchasing 4 total consumable items per character (this means either potions or items that have a finite number of uses (healing ointment, necklace of fireballs, wand of X, etc).
I like to use the optional rules that potions are a bonus action to use/drink, and I enforce constitution saves when two potions are drank within a single hour of each other, with Wild Magic Surges occurring on a roll less than 15.
Challenges are more fair/balanced when no players choose a magic item or character race that provides permanent flight, since that can be detrimental to player party balance in several of the challenges in this dungeon. Normal access to flying through spells like Fly and finite use items is totally fine, its more so the free use issue, as fly can be an appealing/spammable solution to several challenges in the tower, but not in a fun way for either the players or the DM. If players decide they want to spam fly abilities/spells, lower the ceiling in the tower rooms to ensure they are within range of enemies.
To start, begin with the Beyond the Tower scene and have the players introduce themselves around the campfire. Then, the adventure can begin when they approach the exterior of the tower itself.
Some notes about running this adventure:
Short rests will be absolutely necessary, and are encouraged.
Teleportation spells won't work to get in/out of the tower. Let players know this so they don't waste picking plane shift or teleport.
Do not allow a long rest; make this clear to the players from the beginning, as this is designed to be a gauntlet of sorts, making players be creative and ration their resources.
After Level 1, each sequential level of the tower is randomly selected using the Teleporter - Choose Level of the Tower rolltable. Once all levels of the tower have been explored, the players may challenge the final boss, the Arch Lich Diamunda, in her private sanctum.
After Level 1, the players arrive in each room on the yellow teleportation circle, and leave each room via the red teleportation circle. Each room has different challenges and criteria to either get to the exit teleportation circle, or to find a way to activate it through solving a puzzle, traversing the room, or killing monsters and finding the key.
As always, the details included in this adventure are suggested guidelines, and not a requirement. Running exactly as described here will be a balanced experience, but be willing to be flexible and reward player creativity and critical thinking and diverge from the expectations and success criteria described here. At level 18, the players have access to so many powerful spells and abilities that you can't possibly predict what they can do. Most skill checks will need to be quite high (18-23 or so) since players like bards and rogues often have +15 or more to their best abilities.
Through this document, there is various artwork. Share these with the players as they progress, to help them get visuals in addition to your descriptions.
Each level will auto-play musical ambiences. If you engage in combat, switch the playlist to the relevant combat ambiance for that level.