TL:DR Eternals don't die, but if they die they steal the body of another animal
Humans are split into demons and eternals.
Demons die once, for good, no return, they are souless bodies born to survive, reproduce and follow their instincts and intuition like parrot following songs by memory, except demons follow the script in their DNA like a souless computer following different instruction when subject to different commands.
Eternals are born with a new organ, a core which can survive by itself when the body is destroyed, like a seed surviving the death of the apple and also the death of the tree itself.
-If the body is completely destroyed except for the core, then it will start releasing pheromones that make other animals want to eat the core. Animals that eat eternal cores have their DNA hacked to build a new body similar to the old one as they are force fed and they slowly lose control over their bodies.
How does it happen? It is a subconscious process, an automatic calculation like your brain calculating distance, sound and face recognition without you having to ask yourself how far the glass of water is before trying to reach it or if the glass of water is actually a glass of water and not someone's nose.
Eternal cores hold no memory data per se but rember how to ''rebuild'' the old memory pathways, like a computer creating numbers from a QR code scan, this way an eternal core can hold millenia of memory without needing too much space.
So when the brain is recreated, it slowly remembers ''copies'' of the old memories as it develops.
Memories will be incredibly simplified like from ''My first kiss was with Elena by the port as we watched the sun go down and it was the best kiss of my life'' to ''my old body kissed a girl in this port, it was a happy moment''
-if the eternal core is extracted without killing the body, then the eternal core will just seek a new body by being eaten and the old body if still healthy will continue living as a ''copy'' the real conscience is inside the core but body itself is nothing more than vessel that shares memories. For eternals, bodies are nothing but servers.
-Eternals and demons can reproduce but not always capable of producing fertile offsprings and sometimes hybrids can be either considered Devils if the mother is a Demon and the mother is an Eternal or Divinities if the mother is Eternal and the father demon.
-Divinities can force their bodies to ''survive'' almost any critical situation, as long as there is energy to fuel the body and the core is intact then will force their bodies to adapt to anything at incredibly fast rates.
Example: while drowning underwater the core will force all muscles on the thorax to contract above their human limit, even to the point of breaking ribs while trying to breathe in and out water by brute force and will slowly poke holes in the body to release the Co2 like a sponge when being squized.
-Devils do not age and do not die of biological deaths and if they survive long enough their hippocampus will slowly turn into a core and they become Eternals. The speed at which the hippocampus transform depends on the individual, for some it might happen a few days after birth and for others it might happen after a few millenia.
-Eternals if left intact in a semi-destroyed body will do everything to return the body into a functioning enough state where they can gather food and survive long enough to recover.
Semi destroyed Eternals can be almost considered Zombies, they drag themselves around looking for food while trying to not spill their own guts in too many places and struggling to remeber who they are if their brain is damaged
Given the above informations, is there any living organism or system which could be compared in a way to what I listed? some organs that might evolve in a core? some animal that might justify the existance of a core or maybe just a reason?
The question is not : is this possible? cause matematically nothing is impossible but more like a reality check, what in the real world may justify or compare to Eternals?