The modifiers that evolved into [[Horde]] and {{wl|[[http://www.diablowiki.net/Illusionist_(Boss_modifier) Illusionist]] }} seem to have shared properties during development. During Blizzcon demos in 2008, 2009, and 2010 modifiers called [[Doppleganger]] and [[Mirrored]] were seen, each of which seemed to encompass some elements of both Illusionist and Horde.  Only through continuing play-testing did the developers arrive at the precise and different versions of these two similar abilities in the final game.