Defending a house against demons

Question

I'm a fairly rookie GM and I'm running a campaign in which the characters are going to eventually become a group of professional monster hunters.

We are at present low level we are starting off with the basic types of monsters such as a simple "Kobolds took over our mine" quest and segueing into higher level monsters and especially demons at some point down the road.

The players are at some point, as they acquire wealth and some notoriety, going to receive a fortified base (as a safe-house) in the city where the adventure started. I'm trying to find a way that this safe house will be just that, a very safe place for the characters to stay in their off time. But when this will become an issue the villains will be powerful outsiders.

Is there any way that I could protect the house against intrusion or destruction by all but the more powerful of demons?

I would like to make this work so that when the protection is broken (as it will be at some point) it gives the OH S***?! factor to the players because the enemy was strong enough to destroy whatever... countermeasures are in place.

I should point out that as a GM I'm easygoing, this is a small homebrew campaign and we are very much just playing to play.

Answer 1

How about a permanented (or maybe, immovable because it is activated by something too large to move, like an obelisk) Mordenkainen's Magnificent Mansion (PHB p256, Mage's Magnificent Mansion in SRD)? It's a 7th level spell, it is nearly perfectly safe (it can be entered only through ONE portal, which only opens at caster's will). It's a perfect lodge, and if you bind it to the place, it becomes a great safehouse...

Which can be destroyed by Mordenkainen's Disjunction (PHB p255, Mage's Disjunction in SRD), a 9th level spell which automatically dispells all the magic in the area, makes every magic item to make a Will save or be turned into a mundane item and even has a chance of destroying artifacts. The key here is to make sure that all the PC and their gear are at the other side of the Mansion and the demons do not know about that, which will guarantee that nobody would loose any important magic items.

So, in short: Place a statue/obelisk/something else too large to move (or known to lose its power if moved) in the city, let the party activate it to grant them lodging, access to a treasury and the other things you think they need, and let them enjoy that large house for a while. Perhaps it is even activated and deactivated by a treasure the party removed from the dungeon, providing them with a key to the mansion. Then, when you think the time is right, dispel it with Mordekainen's Disjunction (which would be even more surprising if the house had successfully resisted some really hard hits) and let the players suddenly face that high-level encounter 8)

Answer 2

Here are some ideas you could use have some Clerics bless the area with Hallow. This would effectively create a Magic Circle against evil, which can be enhanced with another spell such as Dimensional Anchor to prevent the demons using teleporting through the barrier or detect evil so your PCs would know they are being attacked or evil is nearby. A high level evil cleric could perform Unhallow to counter the barrier and sneak in some demons.

Or option two is to have a powerful Artifact with the spell on it. It would be worth around 20000 Gold in 3.5.

The weakness being that if the creature is not Evil it is not affected. So if a High Level demon convinces (Dominates) a Neutral creature to take the item away, put it in a bag of holding or into some dimension. Then the PCs would be defenceless.

There is also Protection from Evil but that also happens with Hallow.

Answer 3

To protect against Demons/Devils:

Magic circle against Evil

Wall of ...

Hallow

Symbol of ...

Antipathy

Holy Aura

Make any of these permanent with a permanency spell would greatly increase their effectiveness.

To get them involved with Less Savory Folk:

Their (meteoric?) rise to fame for killing lesser evils could attract greater evils. Especially if they're going to be famous as monster slayers, there is a line of logic that villains could follow to kill them so that more monsters can exist. Perhaps a summoner wants to see if his summoned creatures could kill the famous monster-killers?

Certainly, killing off a village of kobolds would attract the attention of kobold clans, and they could enlist the aid of demons to kill those who committed the genocide. Simply put, if you recognize the world as a connected place, whatever the PCs do in one area can affect other things in the area. (As a real-world analogue, you can think of Russia annexing Crimea, and how other countries are in a huff about that.) Given how slow news can travel, it can give the adventurers time to get a base of operations before the retaliation comes.