The Book of Suicidium

As the malevolent entities slowly combined to create such creatures of matter and mind,
A blossoming rot entwined with a thorn; The creator of plagues, a dank star of scorn.
Blessed all the brain stems with a mere ten percent,
But ninety I took from the books document,
dissecting and digging,
researching increasing,
These answers I desperately crave.