The piece of paper appeared in the middle of the air, right in front of Toz, with minimal spatial fluctuations. Since Toz was so deeply absorbed in his grimoire, he almost reacted instinctively and blew apart the letter with a Fireball. But he caught himself in time and snatched the letter out of the air before it could land on the ground.
There were so few words in the letter that it was almost empty, and if it weren't for Toz understanding what the words 'Same circle' meant, he would have been at a loss for what to do. But the letter's message was probably intentional and made in such a way that only someone who knew what they meant would understand.
If it were a stranger, or maybe even a spy, who received the letter without knowing about the magic circle that led to the secret room beneath the base, the letter wouldn't mean anything, even if it ended up in their hands.
After reading the letter, Toz burned it, and not even ash remained, just like he did with the last one.
