Similar to the Demon Domain, or the God's Authority of the Heavenly Father, and the like.
"The Ninth-Circle is called the Grand Wizard... So for the Knight's Ninth-Level, there must be an equally resounding name. Since Holy Domain is the core, let it be called the Holy Sanctuary Knight."
The Holy Sanctuary Knights divide their realms according to the number of Holy Domains comprehended.
They are categorized into four stages: lower, middle, upper, and peak.
These happen to correspond exactly to the four tiered common standards of progression.
Of course, if one were to translate this into wizarding terms—
Upper and Peak would both constitute the "Nine Rings Perfect".
Within the Destruction Heaven, having gotten reasonably accustomed to Ninth-Level Strength (Rune Language)—
Levi's form began to grow illusory, departing from the Six Holy Heavenly Realms.
He has awakened. Now is the time of Destruction!
...
Nora.
Time ticked by, minute by minute.
Blood Battle Command Center.
