D&D 5E Surveillance and Privacy Methods in 5E

[Riley37]

There's a variety of magical ways to observe someone from a distance, or get into position to observe someone, or otherwise observe with less odds of being reciprocally observed. Methods of changing one's appearance are relevant, if that change might enable one to approach or follow a subject who would normally object to the observer's presence/proximity.

Some examples:
(enhanced observation)
Scrying
Arcane Eye
Clairvoyance
Beast Sense
Detect Thought

(spells for getting into position, personally or by proxy)
Invisibility
Disguise Self, Alter Self, True Polymorph
Polymorph
Find Familiar

*** Magic Items
Ring of invisibility, potion of invisibility
Hat of disguise

*** Other abilities
Wild Shape (into a spider, or other animal which may be ignored or overlooked by the target)
Mask of Many Faces

What are some measures one might take to avoid or prevent such observation?
Or to become aware of the observation? Perhaps to locate the observer?
What are some of the most useful anti-surveillance spells and magic items?
What are some useful anti-surveillance abilities (other than spells, other than magic items?)

What methods can be maintained 24/7, or most of the time;
what methods would one use for limited durations, such as temporary privacy for a conversation?

Magic has many, many ways to assist non-magical methods, such as using Spider Climb to reach a location, where one can then perform non-magical, conventional eavesdropping; or Enhance Ability (Eagle's Sight). Let's not bother enumerating ALL those methods, just the most particularly interesting synergies.

Please don't derail the thread.

 

[pukunui]

Off the top of my head ...

Spells:
Antimagic Field
Nondetection
Nystul's Magic Aura

Magic Items:
Amulet of Proof against Detection and Location

 

[Minigiant]

24 hour nondetection cost 3 3rd level slots and 75 gp a day,

 

[Roger]

Blow out the candles and meet in the dark.

 

[bganon]

Counterespionage might also involve Mind Blank, Modify Memory (to really confuse telepathic surveillance), creative use of illusion spells (Mirage Arcane lasts 10 days without concentration and includes tactile elements!)...

Mordenkainen's Private Sanctum prevents scrying, magical travel, etc, and can be made permanent. Then you can cast Guards and Wards on the same location and also make it permanent, for a pretty secure base. Toss a Forbiddance on too if you really want to hurt extraplanar creatures on top of all that.

As far as "nonmagical" counterespionage goes, I think you want good Perception, Insight, and possibly Investigation. Rangers have some scouting abilities that could be useful, and they can have good Wis. Monks can have good Wis too, and while they don't have explicit scouting stuff, they'd make pretty good spy-chasers once a target has been identified (and Shadow Monks can be good spies themselves). Rogues get Blindsense and can choose detection skills for Expertise, and Thieves get UMD.

 

[Greenstone.Walker]

One of the older sourcebooks (I think it was the Castle Guide) talked about using exotic ingredients to stop magic. For example, if you mixed basilisk blood in the mortar then that stopped teleportation in or out of the building. The same idea could be applied to scrying.

For a non-exotic idea, simply sealing a room would stop a lot of those methods. If there is no way into a room then arcane eye, possessed insects, druids shapechanged into tiny animals, and the like just can't get in. Blocking all the light and talking using touch stops scrying.

 

[doctorhook]

Side note: anyone else think the warlock invocation "Visions of Distant Realms" is oddly named? It allows you to cast arcane eye at will, which can travel up to 30 feet per round. That's, like, three and a half miles per hour...and the spell only lasts an hour.

 

[famousringo]

A thin sheet of lead or a thicker barrier of less dense substances can thwart Detect spells.

Divinations are usually restricted to the same plane, so Rope Trick and Mordenkainen's Mansion arguably put you out of the scope of a Scry spell. Demiplane would surely do the trick.