The merciful deeds of a Holy Mother simply did not exist for him.
To be able to absorb the Primordial Chaos Energy, Lin Yi did not kill the demon beast outright but left it with a breath of life. Through experimentation, it became clear that not all demons at any realm could be absorbed by Primordial Chaos Energy.
Only those with Tribulation Strength could be absorbed.
In the entire Spirit Profound Realm, there were only ten known beings of the Human race and Demon Tribe at the Tribulation Transcendence Realm, five from each race. However, in this Demon Domain, through mutual devouring, many Tribulation Fiends had been born.
Of course, crossing tribulation is merely an adjective describing strength. These demon beasts couldn't possibly have undergone the tribulation process, otherwise, those Humanoid Demons with the power of True Immortals wouldn't remain stuck in the Demon Domain.