There's much mentioned of Phelot in those posts about the Fallen, and Phelot is a major character in Myth II. Phelot frees you when you're captured by Soulblighter (Murder of Crows), and is also present when the Deceiver confronts Shiver in The Barrier (Shiver). Shades were loyal to certain Fallen Lords in Myth: TFL, but in Myth II, Phelot seems to do much hopping between Soulblighter and Shiver. However, everything he DOES aids The Deceiver. Also, the above posts support the fact that Phelot previously worked for Bahl'al. Phelot has worked for all of the named Fallen in some way or another.
After vaporizing Shiver's Myrkridia army, Phelot runs as The Deceiver kills Shiver. What became of Phelot? Shades survived the death of Balor, so surely the deaths of Soulblighter, Shiver, and the Deceiver shouldn't seem important.
In Seven Gates, you must kill a shade after watching the armies of The Deceiver and The Watcher duke it out (Come on you cowards, finish me!). The Shade, Scaripant, is loyal to Myrdred. ALL the Fallen have had Shades with them at some time or another, HOWEVER, The Watcher has had the most. As for thrall, all levels are thrall-heavy, no matter what Fallen you're battling. Too keep this post from getting too lengthy, I'll make a seperate post regarding the thrall matter.
In the Crow's Bridge cutscene, I'm sure we're all familar with the "What happened to the bodies?" dialogue. Could Crow's Bridge be the first battle featuring thrall, which were ressurected in Avon's Grove by Phelot?
