Runes had always been Zhao Hai's most long-term and in-depth study. It could even be said to be the most systematic study. Zhao Hai attached great importance to runes because one of his foundations was heaven and earth runes. Therefore, he attached great importance to runes and never gave up on his research. There would always be new runes appearing.
But now, Zhao Hai realized that he had reached a bottleneck in his research of runes. This gave him a headache. This didn't mean that he didn't have enough runes to use, but that his runes were still unstable. His Foundation wasn't stable, which gave him a headache.
Some people would say that a rune had a Foundation. In fact, a rune was not just a simple rune. If it was simple, it would not be able to absorb energy and release energy to become a rune. It was just a useless rune. Therefore, runes were very important and had a Foundation.
