(Heartfelt thanks to 'Cold Shiver ae' for the reward!)
The demonic spear that reversed causality—Gae Bolg!
Its ability manifested as a reversal of cause and effect. With "it must strike the heart" as the premise, it first determined the "effect" of "it must strike the heart," then used the act of swinging the spear as the "cause" to launch the attack.
Because its result—"it must strike the heart"—had already been destined to occur, once Gae Bolg was swung at an enemy, ordinary defenses and evasive maneuvers were utterly meaningless. No matter what, Gae Bolg would definitely strike the opponent's heart!
This effect was practically a curse!
Therefore, calling Gae Bolg a certain-kill spear of inevitable destruction was not an exaggeration at all!
The moment it was swung, the result of "it must strike the opponent's heart" already existed. Even if one defeated Gae Bolg's user first, there was no way to change that result. The heart would inevitably be struck!
To nullify Gae Bolg when it was swung at oneself, one would need luck strong enough to alter fate, making this causality-reversing Spear of Causality incapable of producing the effect of "it must strike the heart." Otherwise, there was absolutely no escaping the curse of having one's heart targeted!
Wu Yan did not think his luck was powerful enough to change the causality predetermined by this Noble Phantasm.
However, Gae Bolg was not much of a threat to him either.
The reason was simple: even if his heart were pierced, as a True Ancestor, he would not be affected in the slightest!
Perhaps the instant the other party pulled Gae Bolg out, Wu Yan's heart would have already recovered completely.
Of course, because Gae Bolg had determined the effect of "it must strike the heart" and was a certain-kill spear,