D&D 5E World building: The forbiddance spell in military application

greg kaye

Explorer
This is intended as a spin-off thread/comment piece to AmandaBarbarian's, World Building: Army building thread within which various arguments have been presented regarding the use of AoE spell casters and use of ground preparation techniques to protect areas.

Among other facilities for protecting areas is the 6th level cleric ritual, forbiddance which, if it were available, might be in demand in times of conflict as a daily ward against teleportation (and either celestials, elementals, fey, fiends, or undead).

(edit: following comment by Oofta below, the 4th level, wizard, non-ritual, private sanctum could also have very prevalent use. I had found forbiddance through a search of ritual spells 🤷‍♂️ ).

It's not concentration so an 11th+ level cleric could cast the 1-day duration spell as often as their stamina, supplies of ruby dust (edit: 1000 gp of unconsumed ruby dust may be required for each daily casting), and abilities to travel between locations permitted. The upshot is that strategic bases (or subsections of those bases) might have perimeters not exceeding an average of 200ft by 200ft and which might have adjacent gateway areas (perhaps in as something like a barbican or a platform of at least 30 ft height) as targets for allies to teleport to. Perhaps temporary, Roman-type, castra forts might adopt 200ft by 200ft average sizes so as to fit with the spell's parameters.

I'd further suggest that, in a world where clerics had access to the forbiddance spell, fortified areas close to established teleportation circles could have average areas of not more than 200ft by 200 ft.

There could also be a potential for shenanigans if your side could somehow manage to discretely cast forbiddance on an enemy area that included enemy teleportation circles or other reference sites they might otherwise try to teleport to.

Anyway:

Forbiddance​

LEVEL 6th
CASTING TIME 10 Minutes Ritual (so I guess that just makes it 20 minutes and they can still do heroes feast)
RANGE/AREA Touch (40,000 ft2)
COMPONENTS V, S, M *
DURATION 1 Day
SCHOOL Abjuration
ATTACK/SAVE None
DAMAGE/EFFECT Radiant (...)

You create a ward against magical travel that protects up to 40,000 square feet of floor space to a height of 30 feet above the floor. For the duration, creatures can't teleport into the area or use portals, such as those created by the gate spell, to enter the area. The spell proofs the area against planar travel, and therefore prevents creatures from accessing the area by way of the Astral Plane, Ethereal Plane, Feywild, Shadowfell, or the plane shift spell.
In addition, the spell damages types of creatures that you choose when you cast it. Choose one or more of the following: celestials, elementals, fey, fiends, and undead. When a chosen creature enters the spell's area for the first time on a turn or starts its turn there, the creature takes 5d10
custom20.png
radiant or necrotic damage (your choice when you cast this spell).
When you cast this spell, you can designate a password. A creature that speaks the password as it enters the area takes no damage from the spell.
The spell's area can't overlap with the area of another forbiddance spell. If you cast forbiddance every day for 30 days in the same location, the spell lasts until it is dispelled, and the material components are consumed on the last casting.
* - (a sprinkling of holy water, rare incense, and powdered ruby worth at least 1,000 gp).


Private Sanctum.
With some similarities to Forbiddence, Private Sanctum has no requirement for concentration but, while it does not have a material cost, as a non-ritual there would still be a limit to its repeated use. With an AoE of up to: a 100ft cube (at 4th lev); a 200ft cube (upcast at 5th level); and a 300ft cube (upcast at 6th level)..., Private Sancum has a superior, per spell level, area and space coverage.
While Forbiddence has a one-way effect that "creatures can't teleport into the area", one potential effect of Private Sanctum is that "Nothing can teleport into or out of the warded area". A ruling as to whether teleportation is possible within the area would, perhaps, depend on a DM. It also protects against the likes of divination.


Private Sanctum​

LEVEL 4th


CASTING TIME 10 Minutes
RANGE/AREA 120 ft (*)
COMPONENTS V, S, M *
DURATION 24 Hours
SCHOOL Abjuration
ATTACK/SAVE None
DAMAGE/EFFECT Control

You make an area within range magically secure. The area is a cube that can be as small as 5 feet to as large as 100 feet on each side. The spell lasts for the duration or until you use an action to dismiss it.
When you cast the spell, you decide what sort of security the spell provides, choosing any or all of the following properties:
  • Sound can't pass through the barrier at the edge of the warded area.
  • The barrier of the warded area appears dark and foggy, preventing vision (including darkvision) through it.
  • Sensors created by divination spells can't appear inside the protected area or pass through the barrier at its perimeter.
  • Creatures in the area can't be targeted by divination spells.
  • Nothing can teleport into or out of the warded area.
  • Planar travel is blocked within the warded area.
    Casting this spell on the same spot every day for a year makes this effect permanent.
At Higher Levels. When you cast this spell using a spell slot of 5th level or higher, you can increase the size of the cube by 100 feet for each slot level beyond 4th. Thus you could protect a cube that can be up to 200 feet on one side by using a spell slot of 5th level.
* - (a thin sheet of lead, a piece of opaque glass, a wad of cotton or cloth, and powdered chrysolite)

Usage
I'd suggest that these spells would encourage the use of square fortifications with 200 ft sides typically so as to cause uncertainty regarding potential magic being used and that prominent personnel might choose to occupy one of any number of similarly appearing fortifications/fortification divisions. Sixth or seventh-level private sanctums might provide area security with efficiency. However, if security is to be given to just one of many similarly appearing fortified areas, I don't think the private sanctum feature to make "The barrier of the warded area appears dark and foggy" would be used. This could make it extremely obvious which camp an enemy should hit with meteor swarms.
 
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Asisreo

Patron Badass
This is exactly the kind of things higher-level D&D should entail.

They make sense when you're looking into the demon king's army or the angelic militia or the united elemental forces, which should be the odds you're up against.

Personally, I don't think there's anything wrong or disruptive about this. It makes sense and shows that not everything can be resolved (like infiltration) with the easy-to-use spell.
 


Oofta

Legend
Building castles was horrendously expensive, some kings practically bankrupted their country building fortifications. Even today we thing nothing about spending millions of dollars on a new highway interchange. Having a permanent forbiddance in many cases is just part of the expense of building a fortification in my campaign world.

Private Sanctum is a similar spell that's even lower level and has no material cost. You have to have someone cast it every day for a year to make it permanent, but it takes that long to build a castle anyway.

Between the two, teleporting in to a secure location is almost never an option.
 


Private Sanctum is a similar spell that's even lower level and has no material cost. You have to have someone cast it every day for a year to make it permanent, but it takes that long to build a castle anyway.

Between the two, teleporting in to a secure location is almost never an option.
SO a 4th level arcane spell that can be made perm over a year, and a 6th level divine one that can be made perm after a month. The Arcane one is lower level, and smaller and skips the damage and password features.

Over all yeah, these two can be used to great effect. Is there a list of spell that over time become permanent until dispelled?
 


greg kaye

Explorer
...
Private Sanctum is a similar spell that's even lower level and has no material cost. You have to have someone cast it every day for a year to make it permanent, but it takes that long to build a castle anyway.
...
Thanks for this m8. I've updated the OP. (y)
 

Note: forbidance is not material expensive on campaign as the materials are only consumed after 30 days in one place. On the march it just takes time.

Each casting covers 0.9 acres. A cleric can waive around their box of ruby dust for two hours each afternoon and have 5.4 acres/2 hectares of teleport-proof (and demon/fey/etc resistant) territory, which is big enough for a roman fortified camp for 1,000-2,000 troops. (The lower end for cavalry or forces with a large baggage train, the high end for infantry with little more than the packs on their back or maybe too tired/rushed to build more camp than absolutely required.)

At the very least, the ruler or high commander of a major campaign and their guard have some defenses against summons and simple teleport attacks (smarter attackers will teleport in 50ft up). Though to be honest, those should have Tiny Huts inside their campaign tents to provide real protection.

 

greg kaye

Explorer
Note: forbidance is not material expensive on campaign as the materials are only consumed after 30 days in one place. On the march it just takes time.

Each casting covers 0.9 acres. A cleric can waive around their box of ruby dust for two hours each afternoon and have 5.4 acres/2 hectares of teleport-proof (and demon/fey/etc resistant) territory, which is big enough for a roman fortified camp for 1,000-2,000 troops. (The lower end for cavalry or forces with a large baggage train, the high end for infantry with little more than the packs on their back or maybe too tired/rushed to build more camp than absolutely required.)

At the very least, the ruler or high commander of a major campaign and their guard have some defenses against summons and simple teleport attacks (smarter attackers will teleport in 50ft up). Though to be honest, those should have Tiny Huts inside their campaign tents to provide real protection.

With the mention of a "sprinkling of holy water", I'd have thought there'd be a similar consumption of the "powdered ruby". Is there any reason to think this wouldn't be the case?
 

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