i kinda have a theory on what just happened to him but i'm not really sure it's accurate
so in the past chapters there was a time that it was mentioned that its poison right? (pls correct me if i'm wrong)
the illusion erin saw while she was holding the black leaf( though i think there might more to it since it was mentioned that it was to vivid to just be an illusion)
and the same illusion was seen again after ainz and erin touched so it's clear that the leaves in the black forest is somehow related to why ainz has the poison, then it suddenly attacked ainz which is actually really confusing since what connection could there be with erin and the black forest and ainz. and the day when erin first saw the black leaves she saw the illusion. so i think that after having contact with leaves erin somehow got connected to the black forest, which gives us a lot of hints about ainz condition, so for me there might be a chance that the black forest can either be a cure or just something that can make the conditions worse.
(what i just explained is just based on my own understanding and opinion about the situation, sorry for the wrong grammar TT)
