Niggross
That key has some serious cheese potential. He can unlock his talent... Allowing him to progress like geniuses. Theoretically if he can imagine it- It should be possible. Since the multiverse theory is true... In his world it's almost guaranteed other power systems exist. Example he can unlock his Aura- since it's possible rwby exists out there. If the key works on his book- He could theoretically allow his hero's to roam free by unlocking their prisons? Or even unlock character slots in his book... Heck that key might even be the answer to theoretically healing Tabitha's mother. He just needs to conceptualize it properly. Unlock her sanity for example.