The spell mighty fortress is very specific about the size and shape of the castle it makes, but not about where walls are connected. Both are 120' square areas with four 20' turrets connected by 80' walls, but the second one you get more interior space and can access your turrets without leaving the outer walls.
The second image is strictly inferior though, enemies can make it to the base of the wall and are then much harder to hit/target. Ideally, you’d be able to make a six sided star fort to fit with the usual hexagonal grid, but that’s up to your dm.
Well, technically it doesn't say your connecting walls have to be straight, just 80 feet long. Not exactly sure how you're going to make them connect up into a hexagon or star out of "four turrets with square bases, each one 20 feet on a side and 30 feet tall, with one turret on each corner", but if you've got a diagram I'd love to see it. 😆
Any self respecting tactician would copy a 15th century actual proven in use fortress. If you are limited to four turrets, then the drawing on top is best.
But you'd have to go outside the walls to get to the turrets. And you're in a situation where you have someone who can cast 8th level spells. I'm not sure this advice is sound. 🤨
Long story short: i like the idea, but the execution leaves a lot to be desired, and it's basically unusable at this point. It's very unbalanced, some buildings are clearly more useful than others, and having one bastion for each player is overkill. It also requires the campaign to stick to a very specific time schedule (a few weeks per level) that I honestly find very difficult to fit in any of the pre-existing modules, and certainly not any of the homebrew campaigns I've played with my friends.
You can make it permanent if you cast it 53 times, and by the time you hit level 15, 500gp for a week of downtime with comfort and security is occasionally worth it. Our druid/cleric regularly casts greater restoration rather than wait for me to prepare remove curse the next morning.
Yeah, fair enough. Casting it enough to make it permanent would be 26,500gp. Which isn't a tiny amount in a general sense, but by level 15 it shouldn't be a major amount of gold honestly. I'd be more concerned with finding that many diamonds frankly.
Still better than the 50,000 gp construction cost and 400 days for a "Keep or small castle" using Building a Stronghold. Actual time spent on labor amounts to a minute per week for a high enough level wizard.
Ten sessions later and the party has complete control of the diamond market. The Barbarian names their mine after his favorite thing, and that's how the My Beers Mining Company starts.
One session after that, they find out that the continental cartel has had decades to entrench their position on the market and can and will field all the manpower that dozens of diamond-producing national branches can field in order to regain control of one lost national mining branch.
Two sessions later, the alchemist is the one who knocks.
You don't even need to homebrew. Spell scrolls exist. It's not unreasonable to think a spell scroll of mighty fortress would be stored away for safekeeping somewhere for a long time before the PCs find it. 👍🏻
