The Grand Array formed by the nine Spirit Pattern Pillars was certainly powerful, but its might was limited by the strength of those controlling the pillars.
Shen Lang had previously considered having the Five War Wolf Commanders, after they advanced to the King Martial Realm, join Yuan Bupu and the others to make a group of nine to control these Spirit Pattern Pillars.
Without powerhouses of sufficient caliber like Yuan Bupu and You Yue Evil Song controlling one of the pillars, the Grand Array's operation would be incomplete. Its power wouldn't be enough to kill an expert at the level of the Demonized Mu Feng, a Half-Step Emperor Martial Realm cultivator.
Shen Lang hadn't summoned the nine Spirit Pattern Pillars with the intention of using the array to trap Mu Feng to death.
He merely wanted to use the Grand Array to corner Mu Feng and compensate for his own lack of speed.
