Ling Xiao cultivated the "Soul Condensation Art" together with the "Sword-Controlling Technique Black Iron Scroll" mainly because the latter required a large amount of soul power to practice.
Nevertheless, even so, with the powerful analytical and practice capabilities of the Mountain and River Martial Soul, within only five days, he had successfully cultivated both the beginner top-tier martial arts, the "Sword-Controlling Technique Black Iron Scroll" and the "Soul Condensation Art" to the Perfect Realm.
However, to cultivate to the Transcendental Realm would likely require some opportunities.
He was in no hurry, as some things needed to be improved through combat. Having reached the Perfect Realm, he was already content.
Upon reaching the Perfect Realm, he didn't hesitate to use the "Bull Demon Technique: Condensing Evil Spirits" to devour these two beginner top-tier martial arts.