You temporarily create an invisible door on hand-worked stone, wood, or metal that is a part of the structure of a house, ship, tower, etc. The door can only be accessed by you and the creatures you willingly choose. Everything else can pass through it as though it doesn't exist. Creatures who use magic to manipulate you into allowing them access, or attempt to use magic or spells to enter are instead sent to a random location in the fey wild? unless it is done via the Wish spell. 

The door creates a hallway made of shadows and ash that is 100 feet long and 25 feet wide. You choose whether space is brightly lit, dimly lit, or in complete darkness. Creatures that are inside the hallway are immune to divination magic cast from outside of the hall. You can create any floor plan you like, but the adjacent rooms can't exceed 60 cubes, each cube being 10 feet on each side. The place is furnished and decorated as you choose, and the Sanctum provides enough food to sustain up to 10 people.

Whenever a humanoid enters the Halls, their shadow detaches from them and becomes a servant made of dark smoke and shadow. They are completely obedient to the owner of the shadow's orders, as well as the casters. Each servant follows its owner and can perform any task a normal human servant could perform, but they can't speak, attack or take any action that would directly harm another creature. Thus the servants can fetch things, clean, mend, fold clothes, light fires, serve food, pour wine, and so on. The servants can go anywhere in the Halls but can't leave it. Furnishings and other objects created by this spell dissipate into smoke if removed from the mansion. When the spell ends, any creatures inside the extradimensional space are expelled into the open spaces nearest to the entrance.