To create the Soul Inheritance Life Card, other than the Soul Cores, Ethan needed two more things.
They are:
[1) 100 High-level Spirit Stones]
[2) 1 Million Life Points]
For Ethan, Life Points were not a problem because he already had 100 million, and even if there was an urgent need, he could just cultivate for a day and earn millions of Life Points.
However, the issue was Spirit Stones.
Before entering the Greenheart Realm, Ethan had nearly three billion low-level Spirit Stones, and to create a single Soul Inheritance Life Card, he needed 100 High-level Spirit Stones or one Million Low-level Spirit Stones.
Adding the 10 Life Cards he created just now, Ethan had created 20 Soul Life Cards until now in the Greenheart Realm and spent 2 Billion Low-level Spirit Stones.
Moreover, he even spent 400 million Spirit Stones to create a perfect environment for the Spirit Plants and another 100 million on the Greenfolk People for their cultivation.
