Hello,

I have a homebrew high magic world where major cities have Teleportation Circles made long ago permanent by repeated (365 consecutive days) casting to facilitate travel and trade. After reading several Sage Advice posts, it appears a simple Dispel Magic spell could destroy these circles.

I don't want to simply decree that they cannot be dispeled because I say so and I want people with enough preperation and ressources to have a chance to do so.

Here's my proposed solution:

Spell with a duration of "Permanent" VS "Until Dispelled", after reading several "Sage Advice" posts, have no practical differences.

 https://www.sageadvice.eu/2015/11/01/can-permanent-magical-effects-be-dispelled/

Dispel Magic:

1- It can only dispel a spell effect, not magic in general. So a +1 sword can't be made mundane by dispel magic. 

https://www.sageadvice.eu/2018/10/02/dispel-magic-is-the-intent-that-you-cannot-target-1-effect-per-pc/

https://www.sageadvice.eu/2016/12/19/can-a-druids-wildshape-be-dispelled-with-dispel-magic/https://www.sageadvice.eu/2016/12/19/can-a-druids-wildshape-be-dispelled-with-dispel-magic/

2- To target a spell effect with Dispel Magic, you need to be aware of the spell effect (as per "Sage Advice" posts).

https://www.sageadvice.eu/2018/10/09/dispel-magic-is-it-possible-to-choose-a-magical-effect-on-a-creature-without-targeting-the-creature/

3- A permanent spell effect can be dispelled unless the description states otherwise. But, IMHO, too easily.

Changes to "permanent/until dispelled" spell effects and their impact on Dispel Magic:

1- What makes a "P/UD" spell effect is the intricate weaving of the flows of magic used to form the spell effect permanent.

2- To dispel the "P/UD" spell effect the caster must have precise knowledge of the intricate flows of magic used, otherwise the dispel is an automatic failure.

3- The original caster has precise knowledge of all the spells he has cast unless his mind has been tampered with or injured.

4- To gain the precise knowledge of the flows, the caster must succeed an intelligence (Arcana) check against the spell DC of the caster +1/casting required to make the spell "P/UD" ("P/UD" Teleportation Circle cast by a 17th level Wizard with 20 intelligence DC 19+365=384).

5- The base DC cannot be reduced but, a caster can reduce the DC bonus by 1 for each consecutive 10 minutes of concentration from a Detect Magic spell, for each spell slot above 1, Detect Magic's duration can be increased by 10 minutes. The study must be continuous and concentration cannot be interrupted or the progress will be lost. The caster can use the cantrip "Encode Thoughts" to transfer his progress to another caster.

6- A 20th level Wizard could use all his spell slots to study the weave of a "P/UD" Teleportation Circle for 890 minutes then use the cantrip Encode Thoughts to transfer his knowledge to a second 20th level Wizard who could then continue the 890 minutes (14 hours and 50 minutes) cycle while the first Wizard rested. After a little over two and a half days of constant casting and concentration, the intelligence (Arcana) DC could be reduced to the base 19.

7- If the check fails, the study was flawed but the cycle can be repeated, if the same Wizards were to try again, they can lower the DC by an extra 5. After further failures, the DC cannot be reduced by more than 5.

8- Only after precise knowledge of the flows is gained can a caster attempt a Dispel Magic spell on a "P/UD" spell effect. Once gained, precise knowledge of a "P/UD" spell effect cannot be lost unless the caster's mind has been tampered with or injured. If the caster fails his Dispel Magic, he can try again anytime he wants.

9- A Wish spell cast by a mage without precise knowledge will dispel a "P/UD" spell effect but only if used has a wish request (with all the dangers of casting a Wish spell) not if used to cast a replacement for a simple Dispel Magic spell.

10- A Cleric could use Divine Intervention to dispel a "P/UD" spell effect only if it was in accordance with the tenets of his deity. A god of life would not allow a "P/UD" Teleportation Circle used to transport wounded soldiers to a hospital to be dispelled even if it was used by the enemy of the Cleric. It is up to the DM to decide what a deity would allow in this case.

If this is a homebrew rule you wanna use, sure, it's your game, go for it.

I most probably will but, I'm also looking for opinions or advice from other DMs.

If we’re talking homebrew, I’d say dispel magic only dispels a permanent teleportation circle for one day. To get rid of it entirely, you have to follow the same procedure that made it permanent to begin with: dispel it every day for a year.

Quote from SagaTympana >>

If we’re talking homebrew, I’d say dispel magic only dispels a permanent teleportation circle for one day. To get rid of it entirely, you have to follow the same procedure that made it permanent to begin with: dispel it every day for a year.

 This is the way I would go. I would use this for things like permanent Mighty Fortress vs Disintegrate as well.

I'm personally fine with there being no distinction between permanent and permanent until dispelled. You still have to succeed on a check above a certain level of spell, and if someone is leaving their magic circle or whatever unguarded long enough that you can make unlimited attempts with dispel magic, they deserve to get it dispelled. Secure your circles, yo.

Even with guards around, Dispel Magic is a 1 Action Instantaneous spell, if cast with a 9th level slot, it automatically ends the effect of the spell.

Almost anyone being able to disrupt the TCircles for a day with a single cast is too much for me, hence the elaborate system.

For Disentegrate, as per definition, it cannot affect magic items. So I would rule a permanent TCircle to be a Magic Item in this case, certanely not a mundane one unlike a permanent Wall of Stone. I'm not sure how I would deal with a Permanent Migthy Fortress.

If you're burning a 9th level spell slot, the most powerful tier of magic in the world available to mortals, you're darn right it should dispel a puny magic circle. That's the level of power of Wish and Power Word Kill. That's like complaining that a Ford Mustang wouldn't stand up to a nuke.

You would need to have direct line of sight without anyone being able to cast counterspell on you to get rid of a circle. If it's that important that dispelling it matters, you put more than just some guards on it. You put it in a locked room, with a mage that knows counterspell. Maybe you put an anti-magic field on it when it's not in use.

If you're talking about throwing around 9th level magic, all bets are off.

Quote from Davedamon >>

If you're burning a 9th level spell slot, the most powerful tier of magic in the world available to mortals, you're darn right it should dispel a puny magic circle. That's the level of power of Wish and Power Word Kill. That's like complaining that a Ford Mustang wouldn't stand up to a nuke.

You would need to have direct line of sight without anyone being able to cast counterspell on you to get rid of a circle. If it's that important that dispelling it matters, you put more than just some guards on it. You put it in a locked room, with a mage that knows counterspell. Maybe you put an anti-magic field on it when it's not in use.

If you're talking about throwing around 9th level magic, all bets are off.

 I like your point about 9th level spells but how would you rule on a Magic Missile cast with a 9th level slot vs Shield cast with a 1st level slot?

When I start to think about these things I usually start to get a headache and then go with the simple solution.

So what would happen if a Powerfull Wizard cast Magic Circle every day for a year with a 9th level slot then another Powerfull Wizard casting Dispel Magic with a 9th level slot? Is that a case of immovable object against an irresistable force?

I said 9th level because it preempted the idea that the TCircle was cast with a 9th level slot. The point is a Dispel Magic spell cast with the same slot as the permanent spell works AUTOMATICALLY, no rolls.

So a Permanent TCircle that took a year to cast (using the base spell 5th level slot) means any 9th level Caster with Dispel Magic can use his 5th level slot to dispel it without risk of failure.

But, I get that you don't see a problem with the way the system works RAW or RAI, I do so, I'll use my system. Again, I'm just looking for more advice and ideas.   

Teleportation circle has no upcast benefit, so there'd be no reason for a powerful wizard to use 9th level slots, spell magic cares about the level of the spell, not the level of spell slot it was cast using. And if they're that powerful, they'd likely just use teleport instead.

I think my advice is you're finding an over-complicated solution to a simple problem. Rather than coming up with complex modifications to the system, encourage creativity in protecting the circle.

In my premise, I state that in my high maic world, some large cities have created permanent TCircles to facilitate travel and commerce.

As RAW and RAI, any 9th level caster with dispel magic and a 5th level slot can with a single action automatically dispel these TCircles.

So even guarded 24/7, it would still be trivial to take out these permanent TCircles the way the current rules work. I could just say that they can't be dispelled but, I also want to make it possible for a dedicated group to have a chance try it even a very slim one. 

BTW Dispel Magic works VS spell level and acording to Sage Advice, the only way to increase a Spell level is to cast it with a higher level slot.

https://dnd.wizards.com/articles/sage-advice/rules-spellcasting

So there may be a reason to cast TCircle with a higher spell slot even if it doesn't directly benefit from it.

It wouldn't be trivial if you had anything beyond mundane guards. If you have a mage willing to cast Tcircle with level 9 spell slots (as you rightly corrected me on), well they're gonna have the means to provide non-trivial protection.

In a high magic setting, glyphs of warding, gazers, anti-magic fields. There's plenty of exciting and interesting ways to secure a magic circle that work within RAW/RAI. I feel that what you're proposing circumvents that room for creativity. 

I like the idea of "counter" spells, let's just spitball here, Anti-Magic field are 1 hour duration Concentration spells but even if they could be made permanent, they would also prevent the circle from working since they block magical travel.

I'm not sure what you mean by Gazers, I assume some form of detection/scrying, by itself, that wouldn't stop the dispel and a simple nondetection spell would cancel them.

Glyphs of Warding or Symbols are interesting but, could you choose the trigger as specific as someone casting dispel magic, if so, would the glyph go off before the dispel magic is cast. With the Glyph going first, you could use a counterspell glyph or a stun symbol (not a death one since collateral damage would be too much).

The problem is RAW, Glyph of Warding and Symbol are one shot, once spent, they are done. You would need multiple glyphs and symbols but wouldn't they all go off on the same trigger?

Also, the glyphs and symbols cover 10 feet diameters, the range of dispel magic is 120 feet, I guess you could use multiple glyphs and symbols to cover 120 feet around the TCircle.

All this hinges on the glyph going off before the dispel magic is cast.

Dispel magic requires line of sight; put the circle in a room and it's protected. Remember:

 "To target something, you must have a clear path to it, so it can't be behind total cover."

A circle in a room with a locked door is safe from dispel magic. Heck, if you covered the circle with a rug, it'll be protected from dispel magic, but still function.

Gazers are beholder like creatures used by mages to protect valuable items and locations.

You're the DM. Just say they found a way that by using more expensive materials or longer periods of casting or multiple mages etc, that they made the circle immune to dispel. Or say there is a 9th level version of the spell - even ones the players could take - that is immune to it. Or perhaps there's a 9th level spell that makes lasting effects immune to being dispelled or can only be dispelled if a certain something is done (such as needed a very expensive specifically made focus?) or that only the caster can dispel it, or, and this is how I would do it: the effect is tied to some stone/portable item and only destroying that item makes it vulnerable (so if they needed to get rid of a circle they still could). Perhaps this 9-level spell that prevents dispelling is applicable to any spell effect with a duration - so other long lasting or permanent effects can be secured. Your players, end game, may even have the chance to join the right factions to learn this secret spell and apply it to their own works.

I fully agree that in the setting having common wizards possibly removing these permanent circles on a whim is inconvenient but I do also agree with Davedamon that you're over-complicating things. There are simpler solutions. 

Glyph of Warding with counter spell a few times I think is a RAW way to stop them being snuffed out. That way you need to spend as much time and effort the plot requires to brute force through the spell defences and it's also a cost to the city to replace those defences if they are attacked.

Made this: Dispel Immunity.

Quote from SagaTympana >>

If we’re talking homebrew, I’d say dispel magic only dispels a permanent teleportation circle for one day. To get rid of it entirely, you have to follow the same procedure that made it permanent to begin with: dispel it every day for a year.

 As far as house rule solutions go, I rather like this.

If the permanent effect is part of the setting lore, all bets are off. Maybe it was made resistant to dispel via wish, divine intervention, a powerful magic item, some ritual not on spell lists, or whatever MacGuffin the DM/Author made up.

what are you trying to protect this against? If your players are not chaos monkeys and would have no reason to dispel the circles, just don't worry about it.

Edit: and if they are chaos monkeys and they do dispel the circle for whatever reason, congratulations, you now have a whole city (or two) trying to hunt you down.