Castle of Black Iron was not a complete world, so there was no Elemental Realm within it. This made it completely impossible for Zhang Tie to enter the Elemental Realm and condense chakras while in Castle of Black Iron. Fortunately, Zhang Tie had also found four Earth Element Crystals on Ent's body. These four Earth Element Crystals barely lasted Zhang Tie three days inside Castle of Black Iron, which was at least some consolation. After those three days, Zhang Tie did not remain idle. Instead, he began practicing the Mind-Splitting Technique of using one mind for five purposes within Castle of Black Iron.
The newly consumed Fruit of Radiance had once again caused Zhang Tie's spiritual energy to surge by a huge margin. His increased spiritual energy was already enough for him to condense a Hand of Spiritual Energy in the Elemental Realm to capture earth elements. However, his ability to use one mind for five purposes was not yet proficient enough. Even if he condensed a Hand of Spiritual Energy in the Elemental Realm, he could not divide his attention to control it. Therefore, Zhang Tie intended to use these days to cultivate his Mind-Splitting Technique to the realm of using one mind for five purposes.
The most difficult part of the Mind-Splitting Technique was the initial stage of visualizing two abacuses and using one mind for two purposes. Once one passed that stage, with the correct method and sufficient spiritual energy, subsequent cultivation would naturally fall into place. It was entirely a matter of steady grinding; once one reached that stage, constant training would make it happen naturally.
Aside from cultivating the Mind-Splitting Technique, Abacus Mental Calculation could also enhance spiritual energy. Therefore, no matter how one cultivated this secret skill, it was absolutely worth the investment and