A ritual involves three parts -- and is like a argument or a case.
Each part details a specific member of The Triumvirate, the proof of Pazuzeus's misdeeds and the contributes a people of the earth gave to imprison the wind spirit.
After Pazuzeus was imprisoned, the parts of the ritual were lost.
If Disciples of the Wind learns all three parts, they can undo the ritual and Pazuzeus will be free.
However, the powers of law can use the ritual to change the proof and the means of imprisonment ot make what the Disciples have learned useless and they will never be able to free Pazuzeus. Since the Disciples of the Wind have two of the three parts, changing the parts is imperative.