Darker with grey fog
Use contrast to make it darker in dark areas and normal light value in light areas.
Marines = Reapers
jetpack = wings or cape
axe = the scythe on his back
rifle = https://encrypted-tbn2.gstatic.com/images?q=tbn:ANd9GcS6S5Cbg6UuEEAqT6rlyNoQwYHFUCvSVFaNqbafPf54r5caY8JcRg
Pistol = http://img3.wikia.nocookie.net/__cb20100811133129/masseffectfanfiction/images/8/8c/Reaper_Gun.jpg
Guns hold in one hand sycth in the other moves faster 50% with sycth out, and slower 25% while holding the guns
Exo = lights from this: http://static.splashnology.com/articles/30_Digital_Artworks_of_Robots/Fireing_at_Reaper_Adam_Kuczek.jpg
and the skelet from this:http://webneel.com/daily/sites/default/files/images/daily/04-2013/23-military-man-3d-robot.jpg
Made into a heavy, creepy robot that hits very hard.
Flashlight = Puts a glow around them that is red and in close around reaper it turns to orange/white.
Aliens = Necromancers/or some unatrual things
Skulk = Ghosts/undead hounds
Gorges = ghost skeleton bug that summons small blue to white colored aura ghosts to help him out.
Lerk = small dragons looking creatures
Fade = Reaper (looks just like a normal reaper/marine) has very little health but instant kill close range if hit behind reaper, (less damage up front, slower leap time longer range cannot attack after teleporting 3s) cannont be dammaged from the front and can mostly be instant killed from behind.
If you not tried to use the same types of Rigid Body then you could use other creatures with the normal human rigid body to make a "real" necromancer for the George class and etc..