Interesting
This was a window into Rune Spark.
It could indeed be summarized in one line, but the implications were both heavy and complicated. It meant several important things.
First, Rune Spark and Aether affinity and Aether control could not be separated from one another.
Second, part of Rune Spark's formation incorporated the very same Kingly aura that Bronze Beasts and above had.
Third, he might very well never touch upon even Rune Essence, let alone Rune Spark, if he couldn't manage to heal the Runes of Earth to a better point than this.
Rune Essence. Rune Vitality. Rune Spark.
These were the three levels beyond Rune Soul, and each one was more difficult to grasp than the last.
However, for whatever reason, Sylas didn't find it to be very difficult. Instead, what was really holding him back was the world around him.