I just realized the show really contributed to the idea of being an avatar to mean just having a cool power by not having martin suffer the consequences of being one or be changed by it or even being hungry. he can just vanish. no don’t worry he is a good person and a human <3 he doesn’t need to feed on fear to vanish into the fog <3 don’t you worry about it
the rules for everyone else is that you have to cause someone to suffer and fear, feed your god or it will feed on you. Jon is haunting people in their nightmares from the beginning, Daisy was straight up hunting people, Melanie was giving into the violence and anger (including threatening Jon). and Martin can just vanish for no reason
the logical answer is that he was feeding on Jon’s loneliness. or not just Jon’s, everyone in the Institute is lonely. except Martin faces no consequences for it, there is no intervention for it, no one performs a non-consensual surgery on him and he doesn’t have to starve. during the safe-house period he doesn’t seem to need to feed at all (and the argument with Jon doesn’t even work here because he isn’t supposed to be lonely any longer)
Martin doesn’t get a hunger or an appetite for human suffering. but he gets to vanish whenever he wants, he has the benefits of the domain (not being tortured). and the closest thing to consequences he gets is that he is cut off from his emotions which falls flat when you remember he later chides Jon for not being good at expressing his own emotions/feelings