Devon's chance encounter with Neist
in a back alley leaves him bleeding out, certain that death is coming for him. When he wakes up several days later in the hospital, he is a changed man. Convinced that he and all of mankind exist only as a stepping stone for demonic evolution, he preaches his ideals to anyone who will listen, all the while hoping to meet his savior again.
Valentin finds him insufferable, and more importantly, dangerous. Unwilling to turn his gun on a fellow human being, he is repeatedly stopped from harming Neist by Devon's over-zealous followers. It doesn't occur to him until it's too late that Neist has no need of such protection.
As far as Neist is concerned, the two of them make delightful companions. To say it has a strange way of showing affection would be putting it lightly.