Terrible Premonition
After absorbing the second soul fragment, Vaan's status underwent great changes. Although the recovery of his Boundless Sea and Sky Aura was most likely his greatest gain, it was not his only gain.
That said, it was definitely his most concerned gain.
Having glimpsed through millions of short reincarnations, Vaan had learned much about Heaven's Envy and Life Tribulation.
The so-called Heaven's Envy was a type of law that had existed since the beginning of time. The purpose of its existence was to control the growth of life and not let it grow aggressively like cancer. This was to prevent the universe from getting flooded with powerful beings capable of destroying worlds.
In simple words, Heaven's Envy was a law of balance and self-preservation, and its purpose was to prune life. Only by overcoming the Life Tribulation would one be allowed to continue living.