Bag of the Between-Worlds (5e Equipment)
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Wondrous item, Legendary (requires attunement)
The bag of between worlds was created long ago, when traveling through dimensions was still in it's early stages. This bag was the experiment of a wizard who was trying to create a portal into another dimension, but the experiment failed. Well to a degree. Instead of taking him to an alternate world, he was taken to a pocket dimensions. He found that this bag could be very useful to him on his travels, but before he could do much with it he was killed and someone else stole the bag. From then on it has been switching hands constantly so who knows who has it know.
Pocket dimension. This world inside the bag has no rooms when first entered, save for the entry way. Instead characters must push against the walls to create rooms, clearing their Strength score in feet per hour, up to the limits defined under rooms and size. The bag can carry 10000 lbs. of equipment. Excess weight can not be brought into the bag.
Rooms. In this pocket dimension, there can only be six rooms at a time.
Size. The first room can be about 1000ft by 1000ft. The second can be 500ft by 500ft. The third will be 250ft by 250ft. The fourth will be 125ft by 125ft. The fifth will 62.5ft by 62.5ft. The sixth will by 31.25ft by 31.25ft.
Safety Features. When the character attuned to the item and up to 12 creatures of their choices are inside the bag, it can't be moved unless already in motion. Also the bag cannot be opened by any outside sources. If the bag is destroyed, all characters and items within the bag inside the room are ejected, landing prone in an unoccupied space within 30 feet of the bag.