How would a PC establish their stronghold in an Outer Plane of appropriate alignment?

[MonkeySage]

Say, I wanna build or take a castle in Hades/Abaddon?

What might I need to do, assuming I have the spells to take me between planes?

And how might it benefit me to take such control on an outer plane, as opposed to some other plane?

What would be the drawbacks?

[LibraryOgre]

Lots of options, few answers.

Creating the actual stronghold would likely take magic... either to simply create the stronghold, or to enslave enough people to make it for you (you're looking at Hades, I assume you consider slavery to be "on the table"). You might also try to seize one from someone who has already done this, but that gets back around to "Lots of work."

Advantages? Not a lot, unless you plan to try to take over a chunk of the plane and rule it as your fiefdom. Your mortal enemies will have trouble reaching you, of course. Your immortal neighbors will alternately ignore you, try to conquer you, or failing that, enlist your aid in their schemes.

[Mastikator]

In addition to the enormous hassle of building a normal stronghold there are additional problems.

Your workers, they're dying! It's Hades
Alternatively, your workers are native to Hades, which is probably worse because how would you even recruit and motivate them to work?

Also there's resources, you need building blocks, so you either need to fabricate them in Hades or transport them to Hades.

I don't know the answer to any of these problems but the first step is identifying​ them.

[Corsair14]

Good luck not being stomped by various fiends and demi-gods and such who don't want the competition. The planes may be infinite in distance but it all belongs to someone or something. Next as said, where to get the labor. You unlikely to have living slaves, so would have to find some way to trade fiends and such for souls to do the work. You would probably have better luck in one of the good planes where the resident power doesn't want to stomp you just because.

[NecroDancer]

You could hire some Devils to help you build the castle or raise some zombies.

[erikun]

If you are magically powerful enough to get to the outer planes (specifically Hades) and construct a stronghold capable of withstanding attack and unwanted intrusion there, then you could presumably create a stronghold anywhere you want. In that case, why the outer planes? Remote spots in the Astral or Ethereal would be just as good and have less aggressive random visitors. Your own personal demiplane would be both better hidden and more secure. Heck, the inner planes would even have less natives randomly upset with you, or at least they would be easier to deal with.

The big problem with Hades, and any other outer plane, is that (presumably) you are not an Outsider and (presumably) your stronghold doesn't benefit the residents of the plane. As such, you're an invader to a large number of hostile forces which consider you a moral outrage just for being there. Add in that Hades itself is rather offensive and it seems very, very hard to manage the upkeep of such a place.

As for how, enough Major Creation and/or permanent Walls of Force (probably the Walls of Force, given where you live) with a healthy number of environmental protection spells would be desirable. Also, some way to produce food, since growing food in Hades is unlikely to be pleasant. You'll also want a quiet portion of the plane and some fairly effective aggressive spells, for when the inhabitants come knocking.

[sktarq]

Really the question is why?

The outer planes (esp Hades and the like) are unpleasant places with ghastly neighbors.

So unless you have both pissed off your mortal neighbors more than the local Hades inhabitants dislike extraplanar invaders and your mortal neighbors are more powerful than those in Hades it's seem like it would increase the headaches in your life.

A particular spot in Hades with access to resources you could export back to the Prime for exceptional profit? That may make the headaches worth it. Devotion to a local diety and hope to buy favor by getting close as a mortal? Religion does make people do funny things and death dieties may make such a thing worth it.

Al that said there is one way to pull this off.

Don't build a stronghold. Don't claim territory. Dig.
Build a dungeon under the stone of Hades. Minimize surface disruption as much as you can. A magically hidden door etc. Even better - bring a landslide down over your door once you are done building-you won't need it. Don't go outside-especially after you finished building. Get your entry/exit point down in the bowels of your dungeon so you never have to go to the surface. Get your logistics set up to come directly into your dungeon (Hades sucks for food generation anyway). This way it will be extremely hard for people to find you when you are there. If nobody knows where you built your dungeon teleporting in is a royal pain. If you don't break the surface and locals don't know you're there they ignore you while the fact you are on another plane gives you protection from many spells. You'd need lots of disintegrate spells, stone shape, spells to make the place livable. I'd recommend using as few people as possible both for logistics issues and the fact that the greatest asset you'd have is secrecy. Honestly a pocket plane is probably easier but if special circumstances are giving you a shot well before/cheaper you could make one of those then this is what I would do.

[Darth Ultron]

Once on a plane you can build a castle the mundane way. You can hire/enslave locals or import your own work crew from somewhere.

Unless your a greater power deity, you won't likely be able to ''control'' a whole plane.

Same draw backs as any castle.

[Mastikator]

Once on a plane you can build a castle the mundane way. You can hire/enslave locals or import your own work crew from somewhere.

Unless your a greater power deity, you won't likely be able to ''control'' a whole plane.

Same draw backs as any castle.

What outer plane locals could you enslave that could do useful things to man a stronghold?

[Keltest]

What outer plane locals could you enslave that could do useful things to man a stronghold?

Isnt it the entire premise of a non-trivial portion of the lower planes that their entire populations are basically conscripted soldiers for various powers either defending the home plane from invasion or preparing to invade? You could practically write up a list of planes, roll a die, and go to that plane with the offer of 'hey, ive got a strategic fortress in Hades that needs a garrison. Don't let anyone bug me while I'm there and you can use it for whatever else you want."