Stronghold Defenses

On June 1, 2006, Posted by , In Campaign Workbook, With No Comments

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While castles, city walls and halberd carrying guards pacing the parapets are standard fare for heroic fantasy, common sense holds that residents of D&D worlds would have created methods to counter threats posed by magical creatures, outsiders, and enemy spellcasters, adapting their defenses to match the available offensive technology.

Presented here are some ideas that you can incorporate into your campaign to make redoubts and cities more defensible against high-level threats and the invasion of intelligent, powerful monsters. Many of these ideas require an enormous expenditure of gold and the aid of high-level spellcasters, but wouldn’t most of the nobility and wealthy merchants in your campaign spare little expense to protect themselves against the greatest threats of their world?


Beyond the standard guards and wards, there are several spells in the Player’s Handbook that can be used to protect important sites. This list is by no means comprehensive, but is designed to illustrate how to think creatively with your magical defenses.

Dimensional lock is an excellent guard against extradimensional intrusion, but has only a 20-foot radius and a visible barrier,

Forbiddance, a great spell for preventing unauthorized magical entry, has a permanent duration and a large area of effect. The casting of forbiddance might well be used as a final seal on a newly finished stronghold, accompanied by a religious ceremony (because it takes a high-level cleric to cast it) or a grand fete to celebrate the consecration and blessing.

Hallow takes a day to cast and only protects a 40-foot-radius area, but can be a powerful deterrent against creatures of evil alignment.

Permanent alarm spells in key locations help guards pinpoint intrusions.

Continual flame spells help light the perimeter of the site’s outer defenses at all times.

Animate plants (entangling) can be cast on ivy-covered walls for added defense against gatecrashers, and permanent walls of stone, walls of iron and walls of force can be incorporated directly into a strongholds construction.

Permanent nondetection cast on specific chambers ensures that a ruler’s secrets remain such.

The various symbol spells (symbol of pain, symbol of death, etc.) are the land mines of the D&D world—cast them in key locations, but be sure to warn the castle staff first.


Conventional medieval castles, with large courtyards and towers, are far more vulnerable in a magical universe than in our own. Flying creatures, dimension door, teleport, and similar threats make it all too easy to bypass heavily defended walls.

Here are some upgrades you might want to incorporate into your non-magical stronghold designs.

In areas with dangerous flying creatures, replace large, open courtyards with extensive sturdy roofing.

Sharp rocks and shards of glass or rusty metal atop a wall can discourage stealthy interlopers.

Roaming guard creatures (dogs or otherwise) can patrol perimeters and alert defenders to any intruders.

Builders might consider an enclosed outer perimeter, almost like a double wall, where traps, guard creatures, and guards could focus their attention and prevent entrance to the inner building. This outer perimeter would ideally extend all the way to the roof of the building, and would also help protect against siege weapon attacks by providing a buffer layer. Should invaders breach the first wall murder holes and arrow slits give defenders the ability to rain oil and projectiles onto the enemy while they deal with the second blockade.

Siege engine teams in critical locations ought to have a supply of magical, silver, and cold iron ammunition on hand for use against special opponents.

Use of summoned or trained web-spinning spiders to place cobwebs in key areas helps protect against invisible intrusion and poses other difficulties to thieves and sneaky attackers.

While it might sound simple, keeping the most vital areas of the stronghold as secret as possible makes it is harder to see and teleport into them.


For large, sprawling cities, place tall watchtowers throughout the area, arming each with loud alarm bells and ballistae in case of a full-scale attack.

These watchtowers can double as bases for teams of trained falcons or hawks whose only function is to spot flying, invisible intruders.

At night, trained owls could perform the same function.

Placing one of these city guard locations in each “neighbourhood” vastly improves response time and intelligence.

In larger cities, guard patrols might try to contain major threats in a manner similar to a fire, responding in strength (platoons of 40+) and evacuating nearby residents in the face of an overwhelming aggressor. Any such response team in a city with a decent economy would likely have a few magic items and spellcasters as well.

Medium to high-level spellcasters or adventurers who live in urban areas would likely be pressed into emergency service in times of need, and may even be obligated to sign a contract of service with the city watch (which would go a long way toward explaining the presence of so many lonely wizards’ towers in the wilderness.)

Many cities practice and hold drills for all types of threats and events, so even high-level characters seeking to rampage through a hostile city may quickly find out that they have bitten off more than they can chew.

If your guards seem underpowered, give them magical items provided by local spellcasters in lieu of taxes.

Guilds, being already organized and highly trained, are a powerful asset in city defense. It’s in everyone’s best interests to have wizards’ guilds heavily involved in defense planning and magical response efforts, and thieves’ guilds might be obligated to help ambush, track, or hunt down criminals who have damaged the city or are trying to flee after committing a major crime (perhaps in exchange for a blind eye to their own affairs).


Underdark dangers are well known to most high-level NPCs who rule towns and cities or live in fortified strongholds.

Beyond the typical dungeon stocked with monsters and guards to help protect against an assault from below, consider the following options for your campaign.

The stronghold has a large cellar completely filled with water, perhaps stocked with dangerous aquatic creatures. Anyone trying to dig into it from below finds their tunnel quickly flooded, alerting the defenders that something is coming.

Acid-filled cellars are a deadlier but more costly option.

Beneath the castle lies a vast cavern lit by everburning torches. The defenders keep watch from the vaulted ceiling 50 or more feet above the floor, ready to rain burning oil, flaming missiles, and spells at intruders.

Permanent walls of iron sunk vertically 30 feet into the ground around the stronghold, combined with similar walls installed horizontally, provide a tough barrier for digging intruders to breach.