Have you ever looked at the wall of stone spell, and started imagining a mage that specialized in construction? I have spent a lot of time imagining this, and here are my findings about how to build a kickass castle quickly and efficiently with spells.
LEVEL AND MULTICLASSING
For this guide, I am going to be assuming a single-classed character of the 10th level in my calculations about how long various methods will take in days, and specifically noting when a higher character level is required to pull off the trick.
A lot of these tricks, while they don’t require cooperation, work a lot better with a PC friend. I’d suggest being a Illusionist Wizard 10+/Knowledge Cleric 2, and making friends with a druid or bard level 5+. If you want it all, got Knowledge Cleric 2/Druid 5/Illusionist Wizard 10+. Any wizard or druid level 10+ is capable of pulling off the majority of tricks listed in here and can build a very respectable castle.
THE SPELL POINT VARIANT
The variant rule for spell points helps this strategy a lot. Typically, you’ll be wanting to cast a particular spell a lot, and the spell points variant rule lets you have the right level slots. I’m going to assume your character is using it. If they’re not, they may wish to consider taking some levels of sorcerer or perhaps warlock (see “getting the right spell slots via multiclassing” below)
BUILDING CASTLES & WALLS
I’ll start off by outlining my favoured method and then considering alternatives or augmentations.
THE GREAT WALL: For this, you will need Wall of Stone (5th level), and Mold Earth (cantrip), and maybe Transmute Rock (5th level). This combination creates an excellent defensive wall, which is 20ft high, 10ft thick, with a 10ft deep 20ft long trench in front of it, that is arbitrarily long. A 10th level wizard or druid can make 500ft of such a wall each day. If 20ft isn’t high enough, you can half the length to double the hight without issue.
First, you’ll need to find a flat patch of rock. If you can’t find one anywhere you need plan to build a wall, you can make some. First, wet a 10ft by 10ft patch of earth to turn it into mud. There are a multitude of magical and non-magical means by which to achieve this. Then, cast Transmute Rock on it to permanently transform it into stone.
Next, we’re going to be casting wall of stone a lot. Wall of stone lets you create ten 10ft * 20ft three inch thick stone panels, if you maintain concentration for ten minutes. It has to be connected to existing stone (one of the other wall pieces or the rock you made with transmute rock). Cast the spell twice to create two 100 ft long walls, sloped slightly towards each other, 10ft apart. from eachother at the top. If you are a wizard of a land druid, you have 74 spell points at level 10 (use arcane/natural recovery to regain 5 first level slots; 2 spell points each). This will let you cast wall of stone 10 times, making 500ft of wall in a day over the course of 100 minutes.
Then, we create the outer trench and fill the space between the walls with earth. Mold earth lets you move a 5ft * 5ft hunk of dirt (1 cube) five feet every 6 seconds. It will take an average of six rounds (36 seconds) to get a hunk of dirt from its place in the trench in front of the wall into the space between the walls. Filling in that wall with dirt/digging the trench will require moving 800 cubes of earth, taking (weirdly) exactly eight hours. So a nine and a half hour work day isn’t bad! Furthermore, because mold earth is just a cantrip, as a 10th level spellcaster you can probably get some apprentices and have them help you. Many hands make light work!
What does this mean in terms of castles? By yourself, you could easily construct a hemeji castle equivalent in three months. If you were really cutting corners (just the perimeter walls 20ft high), you could do it in 25 days. And a 10ft thick wall isn’t coming down easily. You could wall the city of Paris in 221 days.
Now, lets evaluate some other spells and abilities and how they compare to/compliment the great wall method.
GIANT BADGERS: They are a CR 1/4 creature with a burrowing speed of 10ft per round. With longstrider cast on themself before wildshaping into a giant badger, a druid can burrow 20ft per round. Conjure Animals cast at the fifth level (if you read the spell as allowing the player to pick) can summon 16 giant badgers, who can collectively borrow through 160ft of earth per round.
What happens to the earth when you burrow through earth? Who knows. Lets consider three cases.
MOVE EARTH: Move earth is an ok spell for castle building. You cast it for two hours, choose a different 40ft by 40ft space every 10 minutes, and can raise or lower the dirt in it. If you used it as a compliment to wall of stone, one casting of it can fill 480ft of your wall, and dig a 30ft long 20ft deep trench in front of it. It saves you time casting mold earth and gets you a bigger trench, you could use those spell points to cast wall of stone more.
The thing with mold earth is that the dirt you are using has to come from somewhere, and move earth gets over this limitation. It might be useful if you want to build a castle with terraced layers, where you want to raise the dirt-level of the area inside your walls.
BONES OF THE EARTH: The pillars from bones of the earth are permanent. That said, not very useful. This is a poor-man’s wall of stone from our perspective. Plus it is 6th level so it can’t be done at level 10.
MIGHTY FORTRESS: Terrible spell from our perspective. First, it is 8th level. Second, a 500gp diamond is consumed per casting, and it takes a year's worth of casting once a week to make it permanent. You could have four much larger and more customizable castles in that time with the great wall method, and they’d cost you nothing. The free food and servants are nice I'll admit.
WISH FOR A CASTLE + CLONE + SIMULACRUM + OTHER SHENANIGANS: I am undone. If you can find a way to wish for a castle without the 25% chance of loosing wish forever, this is the way to go. If you can’t, then the great wall method is probably better. Plus it is 9th level so you have to be a way more powerful character than the great wall requires.
MIRAGE ARCANE + MALLEABLE ILLUSIONS: First of all, this is a 7th level spell, and malleable illusions is a 6th level arcane tradition feature for the wizard. But if you’ve got access to them it could be useful to castle building. Mirage arcane only lasts 7 days so using it to build a castle outright is off the table. However, if you are worried about the walls you make falling over during construction, then this spell can provide the perfect scaffolding. Change the illusion to bring up supports for your wall of stone after you’ve cast it, then as you fill the spaces between your walls with dirt, change the illusion again to have them disappear.
CASTLE ENHANCEMENTS/MODIFICATIONS
MOAT - CONTROL WATER: Turn your trench into a moat! I am not sure if this really makes your castle more defensible, but it is certainly romantic. How useful the spell is depends on your reading of the “Flood” part, specifically whether the raised water level persists after you have finished casting the spell. If so, make some puddles in the bottom of your trench, cast the spell and fill the moat up. If not, you’re going to have to find a river within 300ft of your moat in order to fill it using this spell. Using the “Redirect water” option, you can stand up to 300ft from your moat and 300ft from a river, and cause the river to flow into it.
DIFFICULT TERRAIN - PLANT GROWTH: What an amazingly useful spell! If you’ve got grass growing in your trench or around your trench, you can cast the spell to make all that grass within 200 ft of where you are when you cast it difficult terrain. The spells Earth Tremor and Errupting Earth also permanently create difficult terrain but not over as wide a radius, though they don’t require any plants.
PERMANENT LIGHTING - CONTINUAL FLAME: This one is pretty straightforward. You don’t have to replace the fuel for the fires on the battlements of your castle. 50 gold per fire is pretty pricey, but lamp fuel and the labor to keep them lit adds up after a while I suppose. You’d need to be a level 3+ cleric to cast this though.
STONE SHAPE: Castles aren't all walls! The wall of stone says the wall can be shaped as you like, but how far that goes is anyone’s guess. Use this for windows, portholes, whatever else you want.
FABRICATE + KNOWLEDGE OF THE AGES: Castles aren’t all walls! With fabricate and knowledge of the ages, if you can get the raw materials (Plant growth can be very helpful for this) you can make anything you want. Turn a pile of iron into a pile of nails, screws, hinges, etc. Turn wood and wool into fancy furniture.
DECORATIONS - MAJOR IMAGE/PROGRAMMED ILLUSION: Cast at the 6th level major image is permanent, and programmed illusion is too (although there is a GP cost associated). Your imagination is the limit! If you want a fancy painting magically animated, or tapestry or suit of armour that waves at you as you walk by, it is only a spell slot away.
DECORATIONS - PLANT GROWTH: Put a garden in your castle and (over-)grow it instantly! Pruning an overgrown rose garden is surely easier than waiting. If you are having a hard time finding the right seeds for your glade of pomegranate trees or rare flowers, try locate animals & plants.
DECORATIONS - AWAKEN: Speaking of gardens, talking trees! It might be some good fun. This is prohibitively expensive unless you’ve got a staff of the woodlands, in which case it is free.
ANNOYING PERMANENT ENCHANTMENTS: Don’t cast Mordenkainen's Private Sanctum every day for a year; just cast it when you need it. Druid Grove and Temple of the Gods are nice but take a whole year of re-casting to be permanent and don’t give you much benefit in a given day You could make four more castles in that time! Guards and wards doesn’t seem that useful. I’d just make a habit of casting Leomund’s tiny hut over my bed each night. Casting forbiddance every day for a month gets you a very nice benefit in preventing planar ambushes. If I had access to 6th level cleric spells I’d certainly consider it.
HALLOW: Hallow is an amazing spell! Protect a 120ft radius circle from celestials, elementals, fey, and fiends, plus a cool bonus effect, and it lasts until dispelled? Yes please! Shame that only clerics (and bards) get it.
LEVEL AND MULTICLASSING
For this guide, I am going to be assuming a single-classed character of the 10th level in my calculations about how long various methods will take in days, and specifically noting when a higher character level is required to pull off the trick.
A lot of these tricks, while they don’t require cooperation, work a lot better with a PC friend. I’d suggest being a Illusionist Wizard 10+/Knowledge Cleric 2, and making friends with a druid or bard level 5+. If you want it all, got Knowledge Cleric 2/Druid 5/Illusionist Wizard 10+. Any wizard or druid level 10+ is capable of pulling off the majority of tricks listed in here and can build a very respectable castle.
THE SPELL POINT VARIANT
The variant rule for spell points helps this strategy a lot. Typically, you’ll be wanting to cast a particular spell a lot, and the spell points variant rule lets you have the right level slots. I’m going to assume your character is using it. If they’re not, they may wish to consider taking some levels of sorcerer or perhaps warlock (see “getting the right spell slots via multiclassing” below)
BUILDING CASTLES & WALLS
I’ll start off by outlining my favoured method and then considering alternatives or augmentations.
THE GREAT WALL: For this, you will need Wall of Stone (5th level), and Mold Earth (cantrip), and maybe Transmute Rock (5th level). This combination creates an excellent defensive wall, which is 20ft high, 10ft thick, with a 10ft deep 20ft long trench in front of it, that is arbitrarily long. A 10th level wizard or druid can make 500ft of such a wall each day. If 20ft isn’t high enough, you can half the length to double the hight without issue.
First, you’ll need to find a flat patch of rock. If you can’t find one anywhere you need plan to build a wall, you can make some. First, wet a 10ft by 10ft patch of earth to turn it into mud. There are a multitude of magical and non-magical means by which to achieve this. Then, cast Transmute Rock on it to permanently transform it into stone.
Next, we’re going to be casting wall of stone a lot. Wall of stone lets you create ten 10ft * 20ft three inch thick stone panels, if you maintain concentration for ten minutes. It has to be connected to existing stone (one of the other wall pieces or the rock you made with transmute rock). Cast the spell twice to create two 100 ft long walls, sloped slightly towards each other, 10ft apart. from eachother at the top. If you are a wizard of a land druid, you have 74 spell points at level 10 (use arcane/natural recovery to regain 5 first level slots; 2 spell points each). This will let you cast wall of stone 10 times, making 500ft of wall in a day over the course of 100 minutes.
Then, we create the outer trench and fill the space between the walls with earth. Mold earth lets you move a 5ft * 5ft hunk of dirt (1 cube) five feet every 6 seconds. It will take an average of six rounds (36 seconds) to get a hunk of dirt from its place in the trench in front of the wall into the space between the walls. Filling in that wall with dirt/digging the trench will require moving 800 cubes of earth, taking (weirdly) exactly eight hours. So a nine and a half hour work day isn’t bad! Furthermore, because mold earth is just a cantrip, as a 10th level spellcaster you can probably get some apprentices and have them help you. Many hands make light work!
What does this mean in terms of castles? By yourself, you could easily construct a hemeji castle equivalent in three months. If you were really cutting corners (just the perimeter walls 20ft high), you could do it in 25 days. And a 10ft thick wall isn’t coming down easily. You could wall the city of Paris in 221 days.
Now, lets evaluate some other spells and abilities and how they compare to/compliment the great wall method.
GIANT BADGERS: They are a CR 1/4 creature with a burrowing speed of 10ft per round. With longstrider cast on themself before wildshaping into a giant badger, a druid can burrow 20ft per round. Conjure Animals cast at the fifth level (if you read the spell as allowing the player to pick) can summon 16 giant badgers, who can collectively borrow through 160ft of earth per round.
What happens to the earth when you burrow through earth? Who knows. Lets consider three cases.
- If the earth you passed through goes directly behind you, this is useless.
- If the earth you passed through just disappears or is compacted into the adjacent dirt, this is excellent for building trenches and underground bunkers (with the aid of some other spells.)
- If the earth you passed through is chucked ~30ft in a direction of your choosing, 16 badgers can replace mold earth for the great wall, filling your wall and building your trench in 15 rounds (a minute and a half)
MOVE EARTH: Move earth is an ok spell for castle building. You cast it for two hours, choose a different 40ft by 40ft space every 10 minutes, and can raise or lower the dirt in it. If you used it as a compliment to wall of stone, one casting of it can fill 480ft of your wall, and dig a 30ft long 20ft deep trench in front of it. It saves you time casting mold earth and gets you a bigger trench, you could use those spell points to cast wall of stone more.
The thing with mold earth is that the dirt you are using has to come from somewhere, and move earth gets over this limitation. It might be useful if you want to build a castle with terraced layers, where you want to raise the dirt-level of the area inside your walls.
BONES OF THE EARTH: The pillars from bones of the earth are permanent. That said, not very useful. This is a poor-man’s wall of stone from our perspective. Plus it is 6th level so it can’t be done at level 10.
MIGHTY FORTRESS: Terrible spell from our perspective. First, it is 8th level. Second, a 500gp diamond is consumed per casting, and it takes a year's worth of casting once a week to make it permanent. You could have four much larger and more customizable castles in that time with the great wall method, and they’d cost you nothing. The free food and servants are nice I'll admit.
WISH FOR A CASTLE + CLONE + SIMULACRUM + OTHER SHENANIGANS: I am undone. If you can find a way to wish for a castle without the 25% chance of loosing wish forever, this is the way to go. If you can’t, then the great wall method is probably better. Plus it is 9th level so you have to be a way more powerful character than the great wall requires.
MIRAGE ARCANE + MALLEABLE ILLUSIONS: First of all, this is a 7th level spell, and malleable illusions is a 6th level arcane tradition feature for the wizard. But if you’ve got access to them it could be useful to castle building. Mirage arcane only lasts 7 days so using it to build a castle outright is off the table. However, if you are worried about the walls you make falling over during construction, then this spell can provide the perfect scaffolding. Change the illusion to bring up supports for your wall of stone after you’ve cast it, then as you fill the spaces between your walls with dirt, change the illusion again to have them disappear.
CASTLE ENHANCEMENTS/MODIFICATIONS
MOAT - CONTROL WATER: Turn your trench into a moat! I am not sure if this really makes your castle more defensible, but it is certainly romantic. How useful the spell is depends on your reading of the “Flood” part, specifically whether the raised water level persists after you have finished casting the spell. If so, make some puddles in the bottom of your trench, cast the spell and fill the moat up. If not, you’re going to have to find a river within 300ft of your moat in order to fill it using this spell. Using the “Redirect water” option, you can stand up to 300ft from your moat and 300ft from a river, and cause the river to flow into it.
DIFFICULT TERRAIN - PLANT GROWTH: What an amazingly useful spell! If you’ve got grass growing in your trench or around your trench, you can cast the spell to make all that grass within 200 ft of where you are when you cast it difficult terrain. The spells Earth Tremor and Errupting Earth also permanently create difficult terrain but not over as wide a radius, though they don’t require any plants.
PERMANENT LIGHTING - CONTINUAL FLAME: This one is pretty straightforward. You don’t have to replace the fuel for the fires on the battlements of your castle. 50 gold per fire is pretty pricey, but lamp fuel and the labor to keep them lit adds up after a while I suppose. You’d need to be a level 3+ cleric to cast this though.
STONE SHAPE: Castles aren't all walls! The wall of stone says the wall can be shaped as you like, but how far that goes is anyone’s guess. Use this for windows, portholes, whatever else you want.
FABRICATE + KNOWLEDGE OF THE AGES: Castles aren’t all walls! With fabricate and knowledge of the ages, if you can get the raw materials (Plant growth can be very helpful for this) you can make anything you want. Turn a pile of iron into a pile of nails, screws, hinges, etc. Turn wood and wool into fancy furniture.
DECORATIONS - MAJOR IMAGE/PROGRAMMED ILLUSION: Cast at the 6th level major image is permanent, and programmed illusion is too (although there is a GP cost associated). Your imagination is the limit! If you want a fancy painting magically animated, or tapestry or suit of armour that waves at you as you walk by, it is only a spell slot away.
DECORATIONS - PLANT GROWTH: Put a garden in your castle and (over-)grow it instantly! Pruning an overgrown rose garden is surely easier than waiting. If you are having a hard time finding the right seeds for your glade of pomegranate trees or rare flowers, try locate animals & plants.
DECORATIONS - AWAKEN: Speaking of gardens, talking trees! It might be some good fun. This is prohibitively expensive unless you’ve got a staff of the woodlands, in which case it is free.
ANNOYING PERMANENT ENCHANTMENTS: Don’t cast Mordenkainen's Private Sanctum every day for a year; just cast it when you need it. Druid Grove and Temple of the Gods are nice but take a whole year of re-casting to be permanent and don’t give you much benefit in a given day You could make four more castles in that time! Guards and wards doesn’t seem that useful. I’d just make a habit of casting Leomund’s tiny hut over my bed each night. Casting forbiddance every day for a month gets you a very nice benefit in preventing planar ambushes. If I had access to 6th level cleric spells I’d certainly consider it.
HALLOW: Hallow is an amazing spell! Protect a 120ft radius circle from celestials, elementals, fey, and fiends, plus a cool bonus effect, and it lasts until dispelled? Yes please! Shame that only clerics (and bards) get it.
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