This is the 14556th most frequent Russian word.
патриаршего
"Patriarchal" (relating to a patriarch or the patriarchate).
The word 'патриаршего' is used in the genitive singular form to describe ownership or jurisdiction of the council associated with the Patriarch.
Этот храм был построен по указу патриаршего совета.
This church was built by the decree of the Patriarchal Council.
Here, 'патриаршего' indicates that the archive belongs to or is associated with the Patriarch, showing possession in a descriptive way.
В музее представлены экспонаты из патриаршего архива.
In the museum, there are exhibits from the Patriarch's archive.
In this sentence, 'патриаршего' modifies 'сада' attributing the garden to the Patriarch, denoting whose property or area it pertains to.