Qiu Tu has been keeping a close watch on the Sixth Sanctuary for a reason.
There are only three Sanctuaries in the Northwestern Region.
The Eighth Sanctuary is Qiu Tu's base; he has reached the level of Sanctuary Leader, so it's best not to make rash moves.
Qiu Tu is actually quite interested in the Seventh Sanctuary, but...there aren't many opportunities.
One must understand that in human society, power alone cannot decide everything. With strength, you can overturn the table, but rebuilding order still requires people.
Unless someone is truly invincible and plans to become a loner, they are certainly subject to the constraints of rules.
Although the major Sanctuaries are part of the Human Alliance, they are in fact independent kingdoms.
Without proper reason, or even...without an invitation from within the Sanctuary's powers, other Sanctuaries' forces cannot easily enter.