Hyperspace keys
There are two kinds of Hyperspace keys, one to send items into hyperspace to store them and another to retrieve them. Items in hyperspace can be retrieved by whoever knows the exact location of the hyperspace bag.
Skull key
Between our own existence and the netherworld of nonexistence lies a gap in the universe.....and with the right tools we can hide a few things there. Using a Skull key, bags containing up to 10 unique items of unlimited quantities can be locked into Hyperspace and out of our existence for safe keeping.
To send items into Hyperspace simply place them in a bag to your feet and use a Skull key.
Skeleton key
Eventually, when we want to recover the bags in between worlds, the Skeleton key unlocks the universal seal. Just make sure you remember exactly where you left it or there might be trouble.... And your bags can be unlocked by other players, if they can find them.