FASA 365 Day 242, Myelencephalon Profundus Oceanus Aranea, (Deep Sean Brainstem Spider) 4-5ft.
Parasitic, Deep Ocean Species.
Attaching itself at the base of the victims skull and attacking the brain matter.
The Victim dies when the brain has gone beyond the capacity to survive… humans only use 10%… so, do the math.
After which the spider allows the body to sink to the bottom, feeding other aquatic life and continuing the circle of life.