D&D 5E What are the best ways to conceal an entrance/door with or without magic?

[FormerlyHemlock]

(Formerly titled "lich bat-cave")

I am making one of the ultimate bosses for my party to fight; a lich with an enormous hidden lair under a city. The problem is he needs it to BE ENORMOUS! He is storing hundreds if not thousands of corpses (including one of a dragon) in order to use for an undead army (I've already handled the issue of only being able to have so many undead at a time due to spell slot restrictions).

Liches in their lairs don't need to do anything special to overcome spell slot restrictions anyway. They recover spell slots with a lair action, which means they have functionally unlimited slots-per-day.

 

[Imaculata]

Besides, the Lich lair should simply be considered a dungeon, and dungeons don't have monster limits. You can toss as many undead in there as you like.

 

[Ahglock]

I just assumed the lich was a serial killer who killed hundreds with finger of death. I might be reading it wrong but comes back as a zombie under your control doesn't seem to have a time or numeric limit.

 

[Celebrim]

The most concealed doors are the ones that are indeed concealed.

1) Covered in plaster.
2) Buried in mud.
3) Bricked over with a wall atop the inner wall.
4) Underwater.
5) Buried beneath breakdown, rubble, or a landslide.
6) Beneath a perpetually burning pile of coals.
7) Tree or other large foliage growing over them.
8) Behind a false door.
9) Beneath 30 feet of snow or ice cover, as for example a glacier.

This is generally more effective than magic, since magic can be detected. The deeper the concealment, and the more difficult it is to move, the more unlikely it is that the secret will ever be penetrated. In some cases, you can put concealed areas in a campaign that no one will ever discover, and you could run thousands of parties through the area and it never be found. A combination of very deep mundane cover and magical scry resistance is probably impenetrable.

So by "best", understand that from a GM perspective, you aren't actually asking what a smart supervillain would actually use to hide something forever. What you are asking is how to hide things in a way that is most fun for the players, and that basically involves not using the best possible designs and leaving behind clues.

 

[crashtestdummy]

Also consider misdirection. Have 'concealed' doors that are revealed with a Detect Magic that lead to traps. The real door is also protected with magic, but use Nystul's Magic Aura (sorry, I don't have the books with me to check the name) that allows you to conceal a magic aura. The players use detect magic, find the door they're supposed to find, and don't think to look for magically concealed doors that you can't detect with magic...

 

[phoffman]

The most concealed doors are the ones that are indeed concealed.

1) Covered in plaster.
2) Buried in mud.
3) Bricked over with a wall atop the inner wall.
4) Underwater.
5) Buried beneath breakdown, rubble, or a landslide.
6) Beneath a perpetually burning pile of coals.
7) Tree or other large foliage growing over them.
8) Behind a false door.
9) Beneath 30 feet of snow or ice cover, as for example a glacier.
....

These are some of of the best way to Conceal doors. Also Trash covering trap doors or sewer entrances, in crypts stack corpses over doors. Basically just cover it with something that would be thematically reasonable. I have found the more it smells and is dirty the covering the more dedicated the players will have to be to find it.

 

[Cernor]

Also consider misdirection. Have 'concealed' doors that are revealed with a Detect Magic that lead to traps. The real door is also protected with magic, but use Nystul's Magic Aura (sorry, I don't have the books with me to check the name) that allows you to conceal a magic aura. The players use detect magic, find the door they're supposed to find, and don't think to look for magically concealed doors that you can't detect with magic...

Nystul's Magic Aura is a great spell. In addition to tricking the party about the presence of doors, you can pull all sorts of nasty tricks; my favourite is to use Nystul's Magic Aura on chalk sigils which resemble Symbols or Glyphs of Warding. When the party sees the door covered in magical sigils which are likely set to explode, they'll probably steer clear and find another route. If that door is truly the only way forward, then they have to make their way through a potential minefield... Not to mention draining their spell slots as they Dispel what magic they can if they try to go through. And if that door is a dummy where the true danger (traps, monsters, etc.) lurks inside, so much the better!

Something else to keep in mind is that a thin sheet of lead stops Detect Magic from seeing things; lead-lined doors would be a pain to make, but a Lich with almost infinite time would be able to do so with ease, hiding all sorts of magical nastiness behind seemingly innocuous doors. However, that depends on how deviously you want to play the Lich... And how dangerous the tone of your campaign has been to date.

 

[Eltab]

Something else to keep in mind is that a thin sheet of lead stops Detect Magic from seeing things; lead-lined doors would be a pain to make, but a Lich with almost infinite time would be able to do so with ease, hiding all sorts of magical nastiness behind seemingly innocuous doors.

A thin sheet of lead, thin panels of wood on both sides and around the edges, iron banding - a magic-resistant door on medieval technology.

 

[Kid Charlemagne]

Something to consider in the hiding of the doors is the planned usage of the doors themselves - does the Lich or any of his minions need to use them to get in and out of the lair? The Lich might be able to teleport in and out, but some of the doors may need to be in a useful place and be able to be opened and closed for lesser minions to move in and out, retrieving and storing bodies etc. That can rule out some of the "sealed door" options like plastering over the door or stone shaping over it.

Along those lines, assuming that the Lich's plan is to use those bodies to in some way threaten the populace, he needs some way to open up a large door for his thousands of undead to pour out into the city. One idea might be to hide that door/gate under a lake/river/pond in the city; the door can be opened underwater (undead don't need to breathe) and the undead can emerge from the depths of the water en masse.