[@Aristo] The Elvkiin and Fae have very different views on nature and what demands worship. On one hand you have the Fae who are plantlike but alive with thought and opinions. On the other hand the Evertrees are giants in their own rights who had given the Elvkiin homes and much needed shelter from the environment. 

I'm sure between the two groups there would be mixed views on how to interact with one another. On one hand you might have Elvkiin who see the Fae as abominations and against their religion. Then you might have Elvkiin who simply don't care that much about them and left them alone. Some Fae would find them to be kin in a way, as they both care about nature. And other Fae would also not care that much, even going as far as saying it would be foolish to worship trees. 

Before the plague they would trade sparingly, and both races would not chose to stay with one another for very long. There have been skirmishes in the past, almost a war between radicals on either side but then the plague came.