This item appears as an ornate iron key, about 6 inches long, etched with complex geometric patterns that seem to subtly shift and rearrange when not directly observed. The key feels cool to the touch.

While holding the key, you can use an action to touch it to a solid, vertical surface that is unoccupied and measures at least 4 feet wide and 9 feet tall (such as a section of wall, a cliff face, or the side of a large boulder). When you do so and speak the command word Tuq'vor(TUK-vor), a shimmering doorway, 3 feet wide and 8 feet tall, materializes on the surface, outlined in faint, silvery light. 

The doorway leads into an empty extradimensional space: a bare room made of smooth, grey stone measuring 15 feet square with a flat, 10-foot-high ceiling. The space exists outside of normal reality.

You can use the room to store items. The room can hold up to 1,500 pounds of material, not exceeding a volume that can physically fit within the 15x15x10 foot space. Items stored must be able to pass through the 3x8 foot doorway. Retrieving an item from the room requires reaching or stepping inside. The key must be on the same plane of existence as the doorway to function.

The room contains no air. When the doorway is closed, the interior is a vacuum. Any creature inside the room that needs to breathe begins to suffocate immediately (see the Suffocating rules). If a creature is suffocating inside when the door closes, the doorway automatically reopens after 1 minute, unless it is opened sooner using the key.

You can close the doorway by using an action to touch the key to the frame of the open doorway and speak the command word again. The doorway vanishes, leaving the surface unmarked. The doorway also closes if you move more than 100 feet away from it.

Overloading: If the room's weight capacity is exceeded, the key cracks audibly, and any items exceeding the limit spill out from the doorway before it snaps shut. The key becomes non-functional, and the doorway cannot be opened again until the key is magically repaired.

Destruction: If the Threshold Key is destroyed, the extradimensional space collapses. Any contents stored within are lost forever.

Interaction with Extradimensional Spaces: Placing this Threshold Key inside an extradimensional space created by a Bag of Holding, Portable Hole, Handy Haversack, or similar item instantly destroys both items and opens a gate to the Astral Plane. The gate originates where the one item was placed inside the other. Any creature within 10 feet of the gate is sucked through it to a random location on the Astral Plane. The gate then closes. The gate is one-way only and cannot be reopened.