Instant FortressEquipment 16
Source Pathfinder Core Rulebook
Price 9,300 gp
Weight light
This metal cube is small enough to fit in your palm. Close inspection reveals fine lines in the dark gray metal, as though the cube were folded thousands of times.
Activate 
command, Interact
Effect You toss the cube on the ground, and it immediately unfolds into an adamantine fortress.
The fortress is 20 feet square and 30 feet high, with adamantine stairs leading up to three sets of battlements at heights of 10 feet and 20 feet and at the top. Arrow slits along the lower battlements and crenelations at the top provide standard cover to anyone within the fortress. There's no roof, leaving an open, 10-foot-square vertical shaft through the center of the structure.
As a magical structure, the fortress has the structure trait. Because it expands outward, the fortress can't catch creatures inside it as a magical structure normally does. Instead, it pushes those creatures back. It can't push a creature into a surface or hazard this way, and stops expanding if that would happen.
The fortress has a single door in the center of one wall on the ground level, and the door appears directly in front of you when you activate the fortress. Provided you're within 100 feet of the door, you can cause the door to open or slam shut and lock by spending a single action to issue a verbal command, which has the auditory trait. The DC to Force Open the door or Pick its Lock is 40.
You can instantly return the instant fortress to its cube form by spending a single action to issue a verbal command, which has the auditory trait. Once deactivated, the fortress can't be activated again for 4 hours.
If the fortress becomes damaged, it can be repaired only with a remake spell or by someone who is legendary at Crafting.
Traits
Something of uncommon rarity requires special training or comes from a particular culture or part of the world. Some character choices give access to uncommon options, and the GM can choose to allow access for anyone. Less is known about uncommon creatures than common creatures. They typically can't be summoned. The DC of Recall Knowledge checks related to these creature is increased by 2.
ConjurationEffects and magic items with this trait are associated with the conjuration school of magic, typically involving summoning, creation, teleportation, or moving things from place to place.
MagicalSomething with the magical trait is imbued with magical energies not tied to a specific tradition of magic. A magical item radiates a magic aura infused with its dominant school of magic. Some items or effects are closely tied to a particular tradition of magic. In these cases, the item has the arcane, divine, occult, or primal trait instead of the magical trait. Any of these traits indicate that the item is magical.
StructureAn item with the structure trait creates a magical building or other structure when activated. The item must be activated on a plot of land free of other structures. The structure adapts to the natural terrain, adopting the structural requirements for being built there. The structure adjusts around small features such as ponds or spires of rock, but it can't be created on water or other nonsolid surfaces. If activated on snow, sand dunes, or other soft surfaces with a solid surface underneath, the structure's foundation (if any) reaches the solid ground. If an item with this trait is activated on a solid but unstable surface, such as a swamp or an area plagued by tremors, roll a @Check[type:flat|dc:3] each day; on a failure, the structure begins to sink or collapse. The structure doesn't harm creatures within the area when it appears, and it can't be created within a crowd or in a densely populated area. Any creature inadvertently caught inside the structure when the item is activated ends up unharmed inside the complete structure and always has a clear path of escape. A creature inside the structure when the activation ends isn't harmed, and it lands harmlessly on the ground if it was on an upper level of the structure.