The Predominated Fruits contained a mysterious power in them that allowed a cultivator to pour in all their respective Laws and condense their Spiritual Incarnation.
The type of Spiritual Incarnation they create would depend on the number and types of Laws they have comprehended and the extent of comprehension they had for every Law. So, it was different for everyone.
As for Krune, just in the name of protecting the wisps, he didn't wish to limit their potential. Hence, his goal was to ensure every wisp was born with a basic Spiritual Incarnation, with almost no attribute whatsoever.
