Юниты "Might & Magic Heroes VI"

what prevents leprechauns from living together with elves?

The fact that they don't exist in Haven.

and let them change the silly name

It's a normal, very pompous name.

Still, there are 400 of them written on Facebook.

Then the game will take place in a time period when Tuidhana died, and the Dark Elves were just expelled from the elven lands, but they haven't encountered the Faceless yet.