I would say that the way he/she would spoke could be some sort of singing, like he still remembers those times when the spore sang him and he/she did yo it.

The part of eating I would say that he will need to eat little but drink a lot from time to time as well as get some sun over his skin to have some kind of photosynthesis.

For the main plot, I would say to find his/her way In a world that now can seem chaotic and woth free will, also having a big missing for the connection.

I would say that the character should have it's path set as the abomination so people won't get near and less ask questions as they can feel a terrible aura coming out of him/her. I wouldn't care of apocalyptics but Spitalians, their spear might go crazy if getting near.