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Thinking about it, if I can truly gain more access to the Original Grimoire, even if not all, I could even be able to get things from my Inventory.
The Tower Master never said about any of such things being a "rule" that I must never violate, so the prohibition of the grimoire or everything else was never stated.
Hence, I could use it, and even if the Tower Master protests later, I can simply use that against their favor, discrediting them for their lack of clarity.
I am sure that they aren't the true boss behind these Trial Towers management, and there must be someone managing these Tower Masters after all.
That's why I believe that they will ultimately not protest, or simply not care. Their personality was cryptic, however, so I doubt I could accurately predict their reaction.
However, after doing all of this, they have yet to protest or attempt to stop me, this means that it is allowed within the Trial.