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The spell Immovable Object when used at 6th level or higher gains a permanent duration. Does this mean that if I have a wizard take enough bricks to make a castle, they could use the bricks to create a castle by casting Immovable Object on each brick?

Theoretically, it should be more than possible, however any creature with a fly speed would have a chance at destroying the castle brick by brick regardless. And I acknowledge that a Wish would be a much more suitable fit for creating a flying castle.

Laurel
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Inuxxus
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    Heavily related: https://rpg.stackexchange.com/questions/92992/is-it-possible-for-a-pc-to-create-a-permanent-floating-castle-or-island/92995 – Joel Harmon May 01 '23 at 17:01

2 Answers2

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Yes.

The spell functions as you described.

However, I do want to flag two additional possible obstacles.

Weight: First, the 6th level up-cast states [emphasis mine]:

If you cast this spell using a spell slot of 6th level or higher, the DC to move the object increases by 10, it can carry up to 20,000 pounds of weight, and the effect is permanent until dispelled.

Depending on the size and design of your floating castle, you may exceed the weight requirement of 20,000 pounds (10 US tons). However, it would appear that this weight restriction applies to each object the spell is cast upon. In theory then, so long as each individual brick is not bearing more than 20,000 pounds of the total weight of the floating castle, the spell should work as intended. So you may need to get creative in your architecture and how you build this castle.

Cost: The spell consumes 25gp of gold dust per casting. Accordingly, you will need a steady supply of gold dust to cast on each brick of your floating castle.

B. S. Morganstein
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    Based on this site, it's about 7,500 bricks just for the walls of a 2,000 sq ft home. That does not include floors, roofs, stairs, etc. A single spell caster has on average 6 slots that can be used to cast 6th level spells (2@6th, 2@7th, 1@8th, 1@9th) plus one 3rd-level for casting fly. So that's 6 bricks per day per caster. There is also mortar and other factors to consider. – MivaScott May 01 '23 at 16:07
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    @MivaScott A more efficient effort would be to create a foundation of immovable objects and then just build normally on top of that. – Michael Richardson May 01 '23 at 16:34
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    It may be worth noting that someone could just dispel the magic. – goodguy5 May 01 '23 at 16:44
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    If immovable object was cast on each individual brick, wouldn't you have to dispel each brick individually as well? – smbailey May 01 '23 at 17:39
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    I like the idea of a wizard thinking they have the big idea to dispel the castle out of the air and having a single brick fall. – Tiger Guy May 01 '23 at 20:06
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    @TigerGuy Or even better, the dispel hits one brick that doesn't even fall because it is cemented to the other ones. – Xavon_Wrentaile May 01 '23 at 23:17
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    @MichaelRichardson, but then you have the problem of weight.. So while you can create a strong foundation, if all the other bricks above it exceed 20,000 lbs, then all of the bricks start becoming dispelled and everything above it tumbles down. So at the very least you'd need to inject immovable bricks throughout the structure so that everything supports the weight. So the foundation is only supporting the layers of bricks up to the layer of IO bricks and so forth all the way up. – MivaScott May 02 '23 at 01:38
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    So you have a castle in the air, made of like 100,000 bricks, cemented together, some of which had Immovable Object cast on them: on different layers, different locations... Good luck dispelling that! – walen May 02 '23 at 08:29
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    Also worth noting that having two immovable bricks on top of each other doesn't help the weight distribution. The top brick will hold all of the weight and the bottom will hold none, at least until it gets to heavy and the top brick falls... – David K May 02 '23 at 12:08
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    @TigerGuy: I like the idea of a wizard thinking they have the big idea to ask residents to cast immovable object daily to make the castle more robust and having a caster target the top of an arch, causing the arch to fail. – Brian May 02 '23 at 13:22
  • @DavidK That isn't clear: "If the object is fixed in the air, it can hold up to 4,000 pounds of weight." - this says if it isn't supported from below, it can hold 4000 (upgraded 20k) pounds of weight. It doesn't say what happens if it is supported from below (a naive reading says infinite?). It seems plausible that it would start pushing down if the limit was exceeded. This is consistent with the fact you can use a strength check to move it without the spell collapsing. – Yakk May 02 '23 at 20:02
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    @DavidK - Given that each "immobile" object and everything it is supporting transmits no weight to anything below it, it seems very possible to "just" have every 10th line of brick or something receive the spell - for the purposes of the limitation each brick is only supporting the weight of 9 regular bricks. – Iron Gremlin May 03 '23 at 00:12
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Frame Challenge

Don't enchant bricks but instead enchant reinforcing bars. Place your first bar in place and thread stone shaped bricks onto it. Thread the next bar through and continue placing shaped bricks until a flat level platform is built from the interlocking bricks.

You can then build on top normally

Alternatively a Daern's Instant Fortress could be placed on enough enchanted discs for a fast and easy floating tower that can be packed up and moved.

Thorne
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