Convergence
If the previous booklet harbored Code 19's secrets, safeguarded by a unique encryption, then it was inevitable that Code 19 would prepare a contingency for certain dire situations.
Perhaps in the event of his demise seeking someone to exact revenge? Or if wronged, to seek retribution?
The information within the booklet was accessible and easily interpretable by Code 19 himself, yet he must have also devised a key for those who found the cipher incomprehensible—a means to "unlock the door" for them.
Could this booklet serve as that very key?
Ali picked up the booklet and opened it.
Its pages were yellowed with age, clearly having existed for some time.
The contents were sparse, mainly comprised of symbols and equations.
By identifying a starting point and embarking on a simple deduction, Ali discovered these to be the derivational equations of a spell matrix.