Regarding rituals of sacrifice, Xu Shu could now claim to be quite experienced and was familiar with the basic rules of sacrificial ceremonies.
Without exception, the standard components of a sacrifice—flesh and blood offerings, Erosion Crystals, and the "Summoning Array"—these three elements were indispensable.
However, the ritual happening in this secret chamber had some oddities, not to mention the glaring omission of the "Summoning Array" step. This omission made them seem very unprofessional.
Without an Array, whom are you summoning?
Even if an Evil God wanted to respond, it couldn't without the Array.
The Sacrificial Array to the left and right was akin to constructing a mysterious channel between "this place" and the "Evil God," piercing through the ethereal space of the "spiritual world" and enabling the Evil God to bestow power, or even allow its will or true form to descend directly.
But now, without an Array, what are you playing at?
Joking around, buddy?