You know i have come up with a reason for why dark elves are carnivorous they come from the island of Incarva which is known for its long nights and winters (With winter lasting almost the entire year and nights lasting about sixteen hours but days lasting about four hours) so thanks to these factors makes farming of crops nearly impossible, meat from the local fauna is there biggest food source (it helps that mammoth are a common fauna in Incarva) however a dark elves diet doesn't only consist of fauna they are known to eat cave mushrooms however they don't get as much nutrition from them as they would from meat