In Eldritch Horror, do epic monsters have to be encountered before non epic monsters?
I think this is taken from the rules of the Forsaken Lore expansion pack. Those rules say:



Additional Rules
The Forsaken Lore expansion adds new rules as described below.

Combat Encounters
During the Encounter Phase, an investigator must encounter each non-Epic Monster on his space before encountering each Epic Monster on his space.



Do note however, that this is the opposite of this question title. Epic Monsters should be encountered last, not first, according to the expansion rule set.