rpg

Having it in a pocket realm in the Astral accessible by a mundane item off to the side in the 'fake' vault filled with low level junk magic items

The pocket realm also does not have any air becuase the BBEG is prepared with their own contingencies, and of course right on the other side of that airless door are a few very persistent golems there to hug anyone who enters

The access to the wizard's vault is an escape room themed after the wizard's life that the players learn of through advertising flyers.

The players will have to decipher clues placed in and outside the room, or interview NPCs, to determine useful facts about the wizard to solve the puzzles (names / # of siblings, favourite pet, first love, best friend's sister's name, etc.) - vary complexity / difficulty of research as needed. The wizard doesn't care if they get in the vault; the wizard wants fame, entertainment, or are appeasing a deal with some entity.

Some puzzles may have lethal/deadly penalties - but really fun ones, like having to reach into a hole for a key, object, or to pick a lock, and it exchanges that limb for that of a fire elemental with no inherent protection from fire given to the rest of the body (temporary or permanent as level dictates); a failed puzzle guess results in a suggestion that elf blood will definitely open this lock (it doesn't, but that must mean you need more, right?); or, just a bunch of dead bats that get dumped on them that later get animated from the dead or spider swarms explode from the corpses after 3 rounds (ghast bat swarm?).

Rooms that fill with water/lava/acid/rum/spikes are always fun. A book just filled with exploding runes in a variety of languages or that is in code and needs to be decoded first before they explode, each explosion larger than the last (book is always unharmed). Intermittent anti-magic zones (spells on even rounds only, temporarily for certain puzzles, spells create random effect of same level from an opposition school, etc.). They repeatedly find clues that point towards a need to kiss (escalate vigor and technique each time, require a certain number of spectators be rounded up, etc.) a statue in the town square, which has no apparent effect.

He re-stocks the vault often by hiring successful invaders for fun adventures that never require morally suspect behaviour of any sort.

Three doors, each leads to 20 doors. The correct door leads to 20 more doors in the correct area, the rest will lead to 20 more doors each, all traps. Some rooms are insulting, with no trap and a single copper on the floor. One of those rooms will lead to 20 more doors, one of which is the correct door.

Lead lined chamber underground, accessible only through a small teleport-only entryway guarded by golems.

Every see the mansions in scooby-doo? I always figured the whole reason D&D dungeons exists is some old wizard needed to project his workshop.

• Weirdly the lab isn't secured but it's a real mess. However, the wizard being paranoid, they bring their job at home,.

• The good old paperwork nightmare sorry you need a pass A38 to enter

• A thrash but fun one, all the notes are tattooed on the back of "slaves", if the players broke in by force, the slave would immediately escape, scattering the note in the city

It looks like a dingy old library. The librarian is actually a genie using mind-control-illusion on everybody but the wizard.

It is a really busy lab where assistants move stuff and build things 24/7. Everybody as an alarm-switch-gadget.

The Eternal Vault is intended for long term storage: Only creatures can get out. No thing, no gear, no spells. The wizard strips naked whenever he needs to look something up in there.

The wizard has an elaborate tapestry on the wall. When under the light of a specific magical candle, you can enter the tapestry to a pocket dimension where everything is woven. There you can find his vault of goodies, literally removed from reality without the light of the candle. If they take the tapestry as a whole, they have to recreate the exact proportions of the wizards study to make it work again.

Artifacts? In a museum, in the"lost and found" box. I tend to go with the wizard that is a bit careless over the super planned one.
The box may or may not be a mimic.

Research room: Wizard Itor uses the back room of his office. The front room contains mops and cleaning supplies (some very magical). The door is even labeled "Jan Itor Supplies"

One of those Bugs Bunny / Yosemite Sam door-after-door-after-door affairs.

Basically have two short stretches of corridor with a door either end. The door at the far end of corridor 1 leads to corridor 2. The door at the far end of corridor 2 leads back to corridor 1.

The mechanisms triggering this are pressure plates along the centre of the corridor 2, skirting along the sides will avoid triggering the plates and allow you to go to the next room.

If a player makes a hole in the door / destroys the door entirely (which I'm pretty sure my players would), they'll see the distant room magically change to the corridor when they step on the pressure plate.

I'd put the lab in a pocket dimension, accessible only through something on the wizard's person. Like a really big bag of holding, but with an air supply.

I'd also rule that pocket dimensions are accessible by an arduous trek through some kind of weirdspace.