Thread Trace Gu

Fang Yuan refines it from his own memories and uses it on the same battlefield where he and Hei Lou Lan inspect a vanishing shadow leopard corpse. By the course of history the Gu should only have appeared three hundred years later. ^{ch. 719}

Appearance

It resembles a small horsewhip of the kind Northern Plains children play with as toys, and its small size is apparent in the hand. ^{ch. 719}

Form and rank

The whip matches toys Northern Plains children play with. ^{ch. 719}

Effect

Whipping the empty air brings out marks. Those marks are dao marks that Gu Immortals and desolate beasts leave for a short time wherever they stop. The marks are extremely weak, and even Gu Immortals paying close attention cannot sense them without this Gu. From the manifested dao marks, an experienced observer can infer path color, rank concentration, how intensely the fight ran, and whether a figure only watched from the side. Gathering the marks shortens their already limited lifespan, and heavy use leaves the whip-like body cracked. After that battlefield use, Hei Lou Lan judges it can serve at least two more times. ^{ch. 719}

Limits

Manifested dao marks last only for a period of time and need plenty of experience to read. Activating Immortal Gu also leaves responding dao marks. In an intense battle many methods tangle those marks until inference fails. On this battlefield few methods were used, so Fang Yuan can roughly understand the situation. Shi Lei and Star Lord Wan Xiang had used mainstream investigative and counter-investigative methods on that field; Thread Trace Gu pierces the gap in those methods. Hei Lou Lan treats the invention as valuable and considers asking whether he will sell it. ^{ch. 719}