How to produce:

• Use command /setblock ~ ~ ~ minecraft:vault[ ominous= true ]
• Use Ominous key on the Ominous vault, and you'll see it doesn't work, it only works with trial key.
  -Get a debug stick which by going into operators tab, place down a vault from creative menu, and and left click 2 times on vault with debug stick until it says selected "ominous" then sneak and right click with debug stick on vault and set the selected "ominous" to true
  -You'll see that the ominous key doesn't work on it, but works with trial key only, it even has particles from normal vault and still gives items from vault.