Royal protection: how to stop high-level magical attacks

[lall]

I’d be like “Less focus on possible inheritance. More focus on j-o-b. And please don’t attack the neighbors. We just had them over for dinner and plan on doing so again.”

[Mastikator]

This is true, but it's also an easy way to alienate players.

"All this cool magic exists! No you can't have it!"
~DM to PCs.

True, but I think there's a way to have your cake and eat it with just a few caveats. Don't make it unavailable to players, make it unavailable to adventuring. You can put the desired magical protections into a large arcane device, and then simply limit how it works. Perhaps it takes days to activate and instantly shuts down if moved even just a little bit, this would incidentally create a weakness in the king's defenses. A lone rogue could sneak in non-magically and just move it, then the evil archmage can teleport in and disintegrate the king.

The players could use the device, just not for adventuring. If they take up base building then this very item might be an object of interest for aspiring basebuilding murderhobos. It won't help them clear dungeons or solve mysteries but it will make their own base of operations more secure.

You can also use it as a worldbuilding and plotbuilding device, perhaps the arcane device was a gift from an archfey in exchange for something from the king, and it requires pact slots to be expended to work, so the archfey also sent a warlock liaison to work the device and make ever more unreasonable demands of the king. Plot twist the king had to surrender his firstborn and the crown prince is actually a changeling!
The queen wants the safe return of the real crown prince but the king doesn't want to risk the ire of the archfey. Now the queen can pose a quest to the players, but completing this quest puts the kingdom in jeopardy. A quest that starts with a moral conundrum and no easy right answers.

[Unoriginal]

I think it's more acceptable when it's tied to something the PCs could access, but realistically won't be able to until the epilogue.

The king's throne room has had ten years of rituals laid on it, preventing any magic except healing magic from working on it. How it was done is a secret, but the king's personal library still has the notes on how it was done-if you can get access to those notes and spend ten years working the magic, you too can have a decent-sized area blocking most magic.

If it's personal power (say, the king has permanent Truesight to make it harder to fool him with illusions) that's a lot more likely to irk players.

In my personal experience, most players are fine when a NPC has a personal power they don't have access to so long as there is a thematic/narrative logic for it.

What they don't like if when the DM makes it look like they're acting like the playground kid who goes "my special power is to have every power" or "my special power is to counter all of your powers."

To give an example from the last campaign I DMed: the players perfectly fine when they entered a place belonging to some Feys and the Feys hit the whole group + NPCs with a very powerful and hard to resist sleep effect. It also was one of the few times an Elf PC got to demonstrate their immunity to magic sleep, so it goes both ways.

[No brains]

I've been thinking about this too, trying to decide what levels of nobility would effectively be what CR of adventure to try to overthrow. There have been a lot of good points already raised in this thread concerning practical use of spells and architecture.

Another good point to consider is that in a fantasy setting is that the 'mandate of heaven' for monarchs might be an actual thing. Defenses to the king do not stop at the mortal level. There are celestials, fey, fiends, or even modrons that have a vested interest in having a king they like in a place they want. This could mean a divine intervention of angels to protect/ avenge the king.

This also means that taking down the king doesn't necessarily have the political repercussions one might intuitively want from it. The policies an assassin were trying to stop are executed on a divine level, making mortal retribution an exercise in cosmic horror. Sure you can kill a rich guy you don't like, but not only will there be another bozo appointed to the same job, but now you're getting tracked down by an angel with truesight and commune to find you wherever you hide and smite judgement upon whatever soon-to-be-tragic cause you were trying to support.

Finally, as a tip in the other direction, if you want to initiate a high-level magic attack and besiege magical defenses, be sure to Planar Bind at least one Babau. Now for the low price of just one 4th and 5th level spell slot and 1000gp, you have 24 hours of at-will Dispel Magic gives you a brute force attack on any level of forbidden hallowed sanctums that they can get line of effect on within 120 feet. I love how this works out because it thematically and mechanically underscores why demon-association is so feared and why the status quo would invest in defenses against cosmic forces diametrically opposed to the status quo. Paladin Smites are counter-bunker busters.

[Slipjig]

Simply building a thin sheet of lead into the outer walls of the palace will stop most Divination spells. Access to even the "public" areas of the palace will be tightly controlled and all guests vetted, and only the most trusted servants are allowed into the private residence, so a Wizard will have an extremely difficult time becoming familiar enough with it to port in.

Every member of the Royal Family has at least one body double (and the monarch secretly has a second that only his wife and the Head of Security know about). The doubles take his place at a majority of public events, and even some private meetings where the other party might not be trusted. There are ten different "Royal Chambers" scattered throughout the palace, and the Head of Security rolls a d10 at bedtime every night to see where the monarch is sleeping. The doubles sleep in randomly-chosen bedrooms. So even if an assassin can locate all the Royal Chambers and become familiar with them, teleporting in blind means he has a 70% chance of finding an empty chamber, and a 20% chance of finding a double.

And that's before we even get to the magical options.

[Unoriginal]

Simply building a thin sheet of lead into the outer walls of the palace will stop most Divination spells.

Which spells would be stopped by the sheet of lead but not by the lead-less outer walls?

[Slipjig]

Which spells would be stopped by the sheet of lead but not by the lead-less outer walls?

You're right, my bad. Looks like Locate Object is the only spell specifically blocked by lead. I was thinking it stopped Clairvoyance and Scrying, too.

[Witty Username]

A brief note that things like body doubles and complex floor plans can reduce the effectiveness of any infiltration, even ones assisted by teleportation.

[Sigreid]

IMO, the best defense is to not be the kind of jerk that needlessly antagonize super high level professional killers. Instead, you have scouts all over the kingdom looking for promising men and women so you can build good relationships with them before they show up riding an ancient dragon with a score to settle. Kings having to build relationships with powerful non royals to maintain their power and survival isn't new.

[Atranen]

Forbiddance and Hallow are nice in theory, but they're shockingly vulnerable to low level dispels. Each has a 1,000 gp cost and extensive cast time (to be made permanent). But, Dispel magic with a third level slot, DC 15 to break.

Your average 5th level caster is at ~50% to dispel with every slot. If they use enhance ability first (and many have access to both), they can get that to 75%. So, the archmage trying to infiltrate does that, or better brings a squad of lower level casters.

You can do many regions of forbiddance (e.g., 5 ft squares each) so it takes many casts, but this becomes extremely expensive. Hallow is spherical and the regions can't overlap--so there will be odd internal structures and some gaps.

The balance favors the offense here, mostly because the designers didn't concern themselves with changing dispel magic for extremely powerful effects. So your best bet is to rely on homebrew magic or creative internal designs (false, hidden, secret chambers).

[Damon_Tor]

Depending on the attitude of the Gods in your setting, monarchs might have a Divine Right to rule, which manifests itself as any of these various protection effects being active even if you don't decide to write in some highish level court mage whose job it is to keep them fresh.

[Witty Username]

Depending on the attitude of the Gods in your setting, monarchs might have a Divine Right to rule, which manifests itself as any of these various protection effects being active even if you don't decide to write in some highish level court mage whose job it is to keep them fresh.

That would be a fun plot twist for an evil party, get hired to kill a lord or such, end up having to fight/outmanuver a proper Archon.

Or the other way a ruller being put on the table for overthrow because they have lost Celestial support. They would probably have to do something pretty evil for that to be a short term consequence though.