my interpretation is that the three main things the fear entities appeal to in order to gain avatars are love, meaning, and freedom.

avatars of the corruption and the desolation seem to talk about love the most. love of the hive, love of destruction. love that corrupts and love that burns. their avatars are often people who have been deprived of love, or whose idea of love has been destroyed in some way.

for meaning, i think the most relevant one is the eye. something you can devote yourself to, something you can worship. the desire for knowledge can define your very existence. this can also apply to the hunt; your purpose becomes catching your prey. hunt avatars are often looking for a reason to feed their violent urgents. eye avatars are just looking for something to believe in.

freedom defines a lot of entities. the vast, obviously, being able to throw yourself into something with no regard for the consequences because nothing matters. if nothing matters, you’re free. same goes for the dark; if you cannot be seen, you can do whatever you want without fear of judgement. these avatars usually seem extremely hedonistic and uncontrolled; their faith in order or the universe has been shaken in some way.