Leafinia's avatar is the Luminous Tree Of Life, as long as it exists, she will not truly die, Sans is inside a coffin that is staying under the Lunar Yin Lake and Yshelia's is an actual clone of her, playing in the bewildering forest that is off limits to anyone except for mindless beasts and the Hope Family.
The mindless beasts might have not developed their intelligence but their strength is not to be looked down upon, their entire body is considered full of treasure in the outside world.
Shadowslash rears them in order to give people food and material resources that can be considered as all high quality, making the lives of the intelligent beings inside Safehaven Paradise a luxury.
Because it was Amethyst that developed these mindless beasts, for them, gaining intelligence is almost impossible, unless they reach the peak rank of this realm, they are restricted by their bloodlines to gain any hint of intelligence.