After Chi Xue, Po Tian, and the others used a few tricks, they successfully lured some cultivators into using their Natal Dan Artifacts as arrowheads. The arrow techniques unleashed by those arrowheads were immensely powerful. Under everyone's attacks, the Ninth Tribulation Cloud was already riddled with holes. At this rate, it wouldn't take long to disperse it completely. Once it was gone, it could no longer interfere with Ling Tian and the others attacking the firmament. There was no doubt that this was their best chance to pierce through it.
Moreover, if the Ninth Tribulation Cloud dispersed, everyone would no longer need powerful attacks to keep the tribulation clouds in a dispersed state. Even energy arrows alone would suffice. That meant no one would have to worry about running out of Entity Arrows. In fact, attacks with Entity Arrows that had undergone multiple impacts weren't necessarily weaker than Merged Entity Arrows. Six- or seven-impact arrows were especially powerful. The reason Merged Entity Arrows affected the tribulation clouds more was that their material was stronger, making them harder for lightning to destroy. Energy arrows, on the other hand, were condensed from energy and were more easily destroyed by lightning.
But if the Ninth Tribulation Cloud was in a dispersed state, it naturally couldn't gather lightning to attack. Even energy arrows wouldn't have to worry about being destroyed then, and their attacks would have a tremendous impact on the tribulation clouds. Any clouds that had just gathered would also be easier to disperse.
Of course, further attacks were still needed to disperse the Ninth Tribulation Cloud completely.
Some cultivators were already using their Natal Dan Artifacts as arrowheads. On top of that, the "plants" arranged by Chi Xue and the others were egging them on. Most importantly, everyone could see that the