From the author:
The Nemesis system in Shadows of Mordor did grab my attention, however.
According to the trailer, enemies will, at times, procedurally develop into antagonists for your hero. This is supposed to be dynamic, in that it will happen differently for each person/playthrough, and these enemies will carry with them marks and memories of your previous battles (and also a healthy lust for vengeance). For instance if you throw an enemy into a fire, half of his face might be burned off, a scar he will carry from there on out. The extent to which your handiwork will be on display remains to be seen.
Full trailer is here:
http://www.ign.com/videos/2014/01/23/middle-earth-shadow-of-mordor-talion-hunts-down-ratbag