The End of the Second Trial
Ling San was still skeptical of everything, but with how kind Xue Bai was acting and the fact that he didn't think the Young Duke would lie to him about such an easily proven thing, he still obeyed.
Pulling out a small, half-foot-long brush, Ling San started to engrave the rune.
To engrave a formation rune, one needed to take the Spiritual Qi of heaven and earth and use it as a sort of ink. Just like in the Law Engraving realm, one would need to use the comprehension of their laws to engrave runes, but instead with Spiritual Qi.
Because this was such a hard thing to do for most people, auxiliary items were created to help cultivators with less talent achieve it. The brush in Ling San's hands was such an item.