Summoning Circles (Promptober 2025 #22)

A common protective circle

Summoning circles (and protective circles generally) come in many forms. Circles made of quickly-spread holy water, rock salt, or silver dust can do in a pinch, but something a little more permanent will provide more power and durability, so a simple gust of wind won't break the circle and let your powerful summoned entity free. How can the everyday wizard or temple cleric set up a more permanent circle?

To start, take some time to design the circle. What form will it take? Do you want a simple pentagram, or an elaborate concentric collection of arcane iconography or divine sigils? What materials will you use to make the circle? Will it be crushed lapis lazuli surrounded by white marble, or worked mithril inlaid in mahogany? How big do you need it? Should you go larger than the standard 10 foot diameter in case you want to summon a demon lord or Archduke of Hell and provide some small amount of comfort?

Once you've settled on a design, figure out what kinds of creatures you want to summon into your new circle. Just elementals, or do you want more broad protections against all manner of extraplanar creatures? Do you want just a barrier to contain them, or should you apply other effects to your summoned targets?

To build and enchant your circle, let's start with the magic circle spell. A 1-minute casting time for an hour duration seems like a slapdash hack for field work. If we look at something like temple of the gods for inspiration, we find that casting the same spell on the same spot for a year will make the effect permanent. Plus, it allows a secondary effect to permanently ride along with the main spell effect.

So let's make this happen at two different power levels.

Starting with a magic circle spell and converting it into something a little more ritualistic, let's say that casting it every day for at least 8 hours will make it permanent until dispelled against a single creature type in about a week. Casting for 12 hours a day instead will bring the time needed down to 5 days. So if you want to protect against multiple creature types, spend another week to cast it again.

For true permanence, spend a year casting the spell every day for at least an hour after the initial "permanent" circle enchantment. If dispelled, the circle will only be suppressed for an hour and pop back after that. The magic seeps into the materials and sustains the enchantment despite attempts to dispel it. It offers protection against multiple creature types after a year's worth of everyday enchantment.

I would allow adding a way to activate/deactivate the circle after a year, as that could open interesting "let's trap the demon here" adventure ideas in an abandoned temple. If you want to add a secondary effect to the permanent circle after this, I say go for it. In looking at the temple of the gods spell, extradimensional interference makes a whole lot of sense.

As for materials, they might add some complications to the casting. For each creature type, I'd want to charge a minimum of 1,000 gp in materials. Labor costs could add onto that total, plus more for the "switch" and additional effects.

Now go forth and make yourself a permanent summoning circle.

Part of the Promptober project for 2025.
I'll also use this in Fellport, so it's listed in the Fellport Almanac as well.