Cultivators generally didn't directly help someone undergoing tribulation, because they feared triggering a chain reaction. The tribulation would then increase in power according to the cultivation level of the person who intervened. Combined with the original cultivator's tribulation, its might might become more than anyone could withstand.
Tribulations recognized the cultivator undergoing them by their soul. Artifact Spirits like Poqiong were also a kind of soul, so entering someone else's tribulation would naturally draw its attention and trigger a chain reaction. That was why, when Ling Tian had said he wanted to use Lian Yue's Advancement Lightning Tribulation to temper Poqiong, Poqiong had scolded him with an irritated spit.
After hearing Poqiong's explanation, Ling Tian scratched his head, looking sheepish. But soon, he grew puzzled and asked, "Poqiong, wouldn't you trigger a chain reaction when you appeared in my tribulation, too?"
"Heh, you've used me during your tribulations before. Did that ever trigger a chain reaction?" Poqiong retorted.
"That's true." Ling Tian murmured. He hadn't asked Poqiong outright, but his eyes were full of the question why.
"You fool, that's because I'm your Natal Dan Artifact." Poqiong laughed. Seeing Ling Tian's thoughtful look, he continued, "That's right. I'm sure you've already figured out why. I'm your Natal Dan Artifact, and our lives are bound through cultivation. My soul is filled with the aura of yours, so even if I appear in your tribulation, it won't think someone is helping you."
"So that's how it is." Ling Tian looked enlightened. He let out a soft sigh. "Looks like you can only be tempered in my Advancement Lightning Tribulations. Sigh, if only you could be tempered in Yue'er's tribulation, too."
"You should be grateful. I'm already lucky to be tempered this early. Other cultivators' Natal Dan Artifacts can only enjoy this treatment