It took me forever to build up my vampires to get Cairn and Hex Wraiths... and they seem to sort of suck? How are they supposed to be "used"? The description of the unit makes them sound like they would wreck low and mid tier units and trade blows with high tier units only if the opposing unit had a magic weapon. Anybody else have any experience with them? What is the "stat modifier for ETHEREAL" ?