Middle Stage

A Gu Master advances by pouring primeval essence into the aperture walls. Middle stage walls are water barriers, also called water walls or a water membrane, ^{ch. 33} where light flows like water and the wall is thicker than the initial stage light membrane. ^{ch. 212 ch. 230} Forming that water wall is the mark of having left initial stage for middle stage.

Green copper primeval essence at rank one middle stage is pale green. ^{ch. 34} It is more condensed than initial stage jade green essence. ^{ch. 80 ch. 212} Used to nurture the aperture, it works at least twice as efficiently as initial stage essence, and a moonblade thrown with it is far stronger than one powered by initial stage essence of the same rank. ^{ch. 34}

A Liquor worm can refine rank one initial stage essence into that middle stage product, so a Gu Master may hold middle stage essence while still cultivating at initial stage. ^{ch. 34} Relic Gu of the matching tier can instead raise cultivation itself by one small realm, for example from middle stage to upper stage. Small realm breaks are treated as a matter of effort and time; large realm breaks need aptitude. ^{ch. 217}

Red steel primeval essence is scarlet at rank two middle stage. ^{ch. 145}

White silver essence at rank three middle stage is blossom silver, with varying amounts of silver in the colour. ^{ch. 312}

A rank four nine eyes liquor worm can purify yellow gold essence by one small realm, yielding yellow gold middle stage essence from a rank four initial stage store. ^{ch. 326}

Purple crystal essence at rank five middle stage is violet purple. ^{ch. 379}

Initial Stage, Upper Stage, and Peak Stage complete the set. The full rank ladder is on Ranks and Realms. Essence by rank is on Primeval Essence.