Building a wizard's tower using 1d20 and maybe some other dice

Get a pen and a paper. Start at the bottom, add a floor and named it "ENTRANCE". Then keep rolling on this table until you're happy, and the continue with the DEBT table at the bottom of this page.

(There's a winding staircase connecting all floors in the middle of the tower, unless you have a better idea.)

1. Find a die that matches the number of floors pretty good, and roll. That floor is now (roll):
   1. Sealed off. There was a breach in reality and a demonic being crawled through. The wizard had to sealed the floor by magical means, but they will only hold for another year
   2. Locked, and the wizard forgot where the key is. It’s actually in the nearest town, but since the key looks like a fountain, it decorates the town centre. The water will from the fountain will unlock the door
   3. Locked, and may only be unlocked from the inside. Someone is living in there, and doesn’t wish to come out
   4. Sealed off. What was previously a door, is now just another brick wall
   5. Occupied by a next-door wizard, who has sealed it off and made it part of her own tower using teleportation magic
   6. Undead. Everything in there is obviously undead, or decorated or made of bones and scary stuff
2. Add a floor on top. KITCHEN. Roll for state:
   1. Never used but fully equipped (pots, pans, plates, etc.). Very clean. A large, cursed knife is stuck in one of the walls
   2. Filthy; used pots and pans everywhere, stacked on top of each other. Three blue mice have taken residence here
   3. Some sort of sentient blob being is cooking food here, constantly. It eats most of it. Give it a name and an allergy
   4. Several squirrels are running around here. Kitchen is filled with twigs, nuts and leafs
   5. A giant is squeezed in here. It’s a good cook but can’t move. It doesn’t mind. Give it a name, a favourite ingredient and an allergy
   6. This kitchen serves both as a crude kitchen and a crude potion lab - it’s impossible to tell what’s food
3. Find a die that matches the number of floors pretty good, and roll (re-roll if you got a result of one). Now, combine that floor with the floor below in all ways possible; thematic and space wise
4. Add a floor on top. STUDY. Roll for major theme:
   1. Books about one-eyed witches, one-eyed frogs, and one-eyed wizards
   2. Books about famous paintings, and what hidden magic they contain
   3. Books and scrolls on top of each other, mostly about other wizards (their names crossed out multiple times)
   4. Books about common potions that somehow all requires birds as an ingredient (multiple beaks can be found in here as well)
   5. One LARGE book, the size of two cows. A children’s tale that works as a teleporter
   6. If the tower doesn’t contain a FUNGUS FARM (#19) yet, add one. This study is all about mushrooms and their effects
5. Does the tower contain a study? If yes, find the study with the lowest room number, and roll:
   1. Add a ghoul that’s walking around licking the books/things
   2. Add a ghost that’s constantly rearranging the books/things
   3. Add a ghoul and a ghost who are chasing each other
   4. Add a ghost that is constantly writing new scrolls, one per hour. 1 in 20 are magical, 1 in 6 are actually useful
   5. Add a ghoul that is constantly writing new scrolls, one per hour. Add a ghost that is constantly proofreading and correcting these scrolls, one per hour. 1 in 30 are magical and extremely potent, but very strange
   6. Roll twice on this table, re-rolling this result, and combine
6. Find a die that matches the number of floors pretty good. Roll twice and connect those two floors on the outside by means of:
   1. Wooden staircase, crude and unreliable
   2. A floating disc that constantly travels between those two in some irregular, slow pattern
   3. Clinging, green vines
   4. Copper chute (one-way slide)
   5. Twenty small birds; they’re incredibly strong. 1 in 6 chance they will drop you off somewhere else
   6. A spinning pentagram floating in mid-air; 1 in 6 chance this will teleport you somewhere dangerous
7. Add a floor on top. PRIVY CHAMBER (TOILET). This floor is projected out a bit. Roll:
   1. Add a river next to the tower. The waste from the privy falls into it. Give the river a name, and a ferry man further down with a name and a phobia that relates to flowers somehow
   2. Add a waterfall next to the tower. The waste from the privy falls into it. The waterfall seems to go on forever, and winged beasts from downstreams sometimes lands on the tower roof
   3. Some strange magic inside the privy is turning everything that goes through the toilet into different kinds of seeds. Down below on the ground, right next to the tower, all sorts of trees and flowers are growing
   4. The privy is locked. The wizard can’t remember why and doesn’t care, but suspects a cousin
   5. Exiting the privy (e.g. opening the door again) will always lead to the outside, as if stepping out of the entrence
   6. Rare spell books can be found in here, but with torn out pages
8. Add a floor on top. TELEPORTER. Roll:
   1. Salt circle on floor, but doesn’t work. There’s meat in the corner
   2. Salt circle on floor. Teleports to highest floor number
   3. Salt circle on floor. Teleports to lowest floor number
   4. Red pentagram on wall. Once per week, there’s a 5% risk/chance a horned creature steps through and sets up a nest on this floor
   5. Red pentagram on floor. Teleports to floor below, since it’s really just a trap door
   6. Silver arch in middle of floor. Teleports to another wizard’s tower, inside a closet
9. Find a die that matches the number of floors pretty good, and roll. Now add a BALCONY to that floor. If the floor number is even, it’s an open balcony, otherwise it’s a closed one
10. Add a floor on top. BEDROOM. Roll:
    1. Extremely simplistic: a bedroll on the floor. A wide beewax candle is halfway burnt on one side, and a pile of bulky books are stacked on the opposite side
    2. Several made beds are here, of different sizes, none which belongs to the wizard, who sleeps on the floor where ever she gets tired
    3. The bed is made from a large tusk, hollowed out and made “comfy”
    4. This room is empty, except when the wizard enters to sleep. Then, fifty cats enters through the window, and form a bed of sorts, allowing the wizard to sleep there. They will wake her up in the most rude way every morning
    5. The bed is just a bookshelf tipped over, shelves removed. The wizard has stitched together torn out pages to form a blanket
    6. Moss is covering the entire floor, although the furniture is still underneath somewhere. The wizard falls asleep where ever
11. Add a floor on top. LARDER. Roll 2 times:
    1. Meat of unknown origin is covering this room, hanging from hooks everywhere, some of which is still twitching
    2. Mostly fish of bright colours. 1 in 20 are of low magical potency
    3. Flour, sugar, spices. Just dry ingredients. 3 in 6 are of fey origin
    4. Jams. Small glass jars filled jam. All of low magical potency, but only 1 in 20 actually taste good
    5. Broken pottery, but no food. 1 in 6 have rune inscriptions all over them
    6. Lard, kept in clay pottery
12. BRANCH OFF. Find the floor that’s more or less in the middle of the tower, and add a passage there straight out (to the right or the left), and start a new tower there. Add only new floors to that new tower part from here on.
13. Add a floor on top. STORAGE. Roll:
    1. Tomes that lost their magic, or the lettering is too small to read
    2. Covered paintings leaning against the wall. 1 in 6 are trapped adventurers and animated
    3. Chairs, book cases, tables, etc. All broken in exactly the same way, all stolen
    4. Empty wooden barrels, stacked without reason
    5. Crystals shaped like pyramids, the size of chairs, all glowing faintly and humming
    6. Empty glass vials, in sizes ranging from a thumb to half an arm
14. Find a die that matches the number of floors pretty good, and roll. Then roll on the table below and apply to that floor:
    1. A large spider has taken residence here, spinning webs everywhere. It’s hostile. If there’s already a spider on this floor, have the new one battle the first one
    2. A wizard has occupied this floor as his own, “not so very tall” tower. He’s friendly, low level and nuts. Casts summoning spells of the woodland kind. Never leaves.
    3. A magical portal to some nearby lake can be found in the ceiling. It constantly drips, and fish rains down at least twice per day
    4. A miscast spell has made everything in here half as big
    5. There’s a mirror here that works as a portal. It will always lead to the top floor
    6. There’s a lot of barrels here, where plants and edible things are growing. A tiny cloud is circeling the ceiling, keeping everything wet and fresh
15. Add a floor on top. DISPLAY ROOM. Roll:
    1. Different types of brains in glass jars on high pedestals. Only a few seems to be of human origin
    2. Caged kitchen utensils that behavs like different types of animals (small birds, cats, lizards, etc.)
    3. Decorated mirrors, one for each floor in this tower, that shows what’s going on in there
    4. Gnarly staves, of the very old kind, suspended in mid air, hovering in place. One is chatty
    5. Metal trinkets inside small glass domes. A plaque next to each dome tells its story
    6. Pedestals scattered around the room, each holding a single coin from a now long lost empire
    7. Butterflies in cages, stacked on top of each other. 1 in 20 is of fey origin, and kept prisoner
    8. Fossils, arranged and put together using best guesses. Looks terrifying, but the wizard is proud and certain of her work
16. Does the tower have at least one balcony? Find one that hasn’t got a rope hanging from it, and add one. The rope must reach the ground. It’s alive, so give it a name and an agenda
17. Add a floor on top. EXPERIMENTS. Roll:
    1. Man-sized eggs covering the floor. Some cracked, some empty. A desk with notes and seeds in the corner
    2. Humanoid creations, children sized, built from scrap metal and old furniture. 1 in 6 reacts when approached
    3. Tomes are flying around the room. The book shelves are rebuilt to resemble trees. They crap tiny scrolls of minor magic
    4. A squirrel in a wizard hat has built what looks like a replica of the tower itself, including the surrounding area outside. It has constructed a tiny teleporter which goes outside, through which it fetches its materials
    5. Perpetual motion machines. Some small as an egg, two or three large as a horse. Water flowing, cogs turning, wooden wheels turning… It’s not obvious what they are doing, but 1 in 6 are producing magic melodies as a biproduct
    6. Devices for countering spells. All clumsy, but always works. One use, and will blow up (causes small damage to the user). Looks like nothing else
18. Does the tower contain a STORAGE? Choose another floor at random, and create a small pixie servant that’s currently moving stuff out of one floor into the storage. Give it a name and an allergy
19. Add a floor on top. FUNGUS FARM. This roll looks like a tiny forest indoors. Roll:
    1. If the tower doesn’t contain an EXPERIMENTS floor yet (#17), add one now. The mushrooms growing here are plucked and used (crucial) for the experiments
    2. The mushrooms here are edible, but alive. When they are fully grown, they pluck themselves and start running around, building stuff. Friendly but annoying. Talkative
    3. The mushrooms here are growing out trough the windows. A settlement of small pixies have taken residence here, carving houses and roads in the mushrooms
    4. Three skinny trolls are living here. They are living off the mushrooms and can see two days into the future. They are extremely friendly and mellow
    5. Extremely potent magical mushrooms if prepared properly. Word is going around, and the wizard keeps this floor tightly locked
    6. A single mushroom is growing here. It takes up the entire floor. It’s sentient and will eat anything. It attracts prey using scent. The wizard doesn’t know how to deal with it, but it’s starting to become a problem
20. Add a floor on top. LEGATION. The wizard has given up this floor for a minister from somewhere else, in exchange for goods, secrets and other juicy stuff. Roll:
    1. Representative from the fey. Not the brighest. Wears glasses without glass
    2. Representative from a tiny plane of lawful demonic creatures. Trades in lies
    3. Representative of prismatic beings, e.g. that lives in rainbows. Shortlived but have lots of coins, and easy aerial bridges when it’s raining
    4. If the tower doesn’t contain a FUNGUS FARM (#19) yet, add one. Representative of mushrooms. Trades in gossips heard from camps all around forests everywhere, but only if the wizard keeps her hands off the mushrooms in the FUNGUS FARM
    5. Representative from the plane of nightmares, a fanged, motionless shadow in a corner. Hasn’t spoken yet, but haunts the wizard in her dreams, terrifying her senseless but always with a hint of something important just before she wakes up
    6. Representative from the plane of all things metal and logical. A large metallic box, that hums, clicks and whirrs. Actually, this minister is missing a screen, but the wizard doesn’t know that, and is still waiting for an answer

DEBT TABLE
So, now you have a tower, with a certain numbers of floors. Let's see how the wizard managed to pay off this endevour:

1. Nothing to worry about, no debt here. The wizard found the tower and managed to overtake it by turning the previous owner (also a wizard) into a frog (put the frog at the top floor - it's alive and has allies looking for it)
2. The wizard built the tower using a work force of mostly undeads, conjured from a large graveyard not far from here. She dissolved the entire work force when the tower stood complete, so bones and rotting bodies are scattered all around the tower's vicinity
3. The wizard borrowed a large sum of coins from her former academic friends, with a promise that she'd pay it back in full. This was several years ago
4. The wizard formed a pact with a shadow that manifested in her dreams several years ago. The tower rose from the ground, fully built and populated, but whatever the wizard promised she hasn't kept it
5. The wizard has stolen each floor from other buildings, using an extremely powerful spell that relocates entire buildings (or, parts of them). She's wanted in as many cities and towns as there are floors in the tower
6. The tower is actually a space faring vessel, and the wizard is only here for a short visit, but she stole the vessel prior to coming here, and there's an armada out there looking for her