This was an ability Zero Burial had discovered after resurrecting the five through Impure World Reincarnation. This Qianshan Guard was a rare spirit-grade secret art of Thousand Mountain Valley, with exceptionally strong defensive power. It could be cast by one person or jointly by several; when used together, its defensive strength multiplied. Thus, it was a mandatory technique for Thousand Mountain Valley's powerful cultivators.
Without question, all five resurrected through Impure World Reincarnation had cultivated this technique and attained high mastery of it. Therefore, Zero Burial had greatly amplified its power through their combined casting. At the same time, he had discovered a secret to deploying this formation from the five of them.
That secret was that, when casting it together, the casters could form an array and use a magic treasure as its core. Then, even after the casters were killed, Qianshan Guard could persist for some time. In other words, they could use their own lives to maintain the formation until their bodies exploded!
This discovery greatly interested Zero Burial, which was why the five had jointly cast Qianshan Guard today. For the formation's core, Zero Burial had directly used the immortal artifact Primordial Chaos Pearl. With this treasure added to the mix, both the formation's defensive strength and duration underwent a qualitative leap. That was also the key to its ability to withstand Mo Yunfeng's attacks.
Beyond that, the reason this formation was so immensely powerful lay in the inherent advantages of Impure World Reincarnation itself: unlimited chakra, and the inability to be killed by ordinary attacks!
That was why, even after the five had been killed, the formation remained. Then the casters revived, reinforced the formation once more after reviving, and repeated the process like an endless cycle, forming an Absolute Defense unique to the five