OK, might as well restate my theory so people can laugh at it.
The Myth2 Shiver looks different and has a different personality from the TFL one (she still does the vanity thing, but she's a lot more ferocious and unthinking.) She also "forgot" all her major battle spells, including the Whisper Dream.
This makes me think that the two Shivers *are* different. Not reincarnations, not alternate personalities--just different people. After all, according to GURPS, Ravanna and Shiver were always thought to be separate Lords. Only after her conversation with Myrdred did people start wondering.
I believe that Soulblighter never successfully revived Shiver. Ravanna, the Voiceless One, who survived the end of TFL unnoticed (she was always the best Fallen Lord at stealth), took her place and assumed her identity. Why, I don't know; but I'd guess that Soulblighter wasn't particularly interested in working with Ravanna. So if she wanted a piece of the Dark pie this time, she had to take on the identity of someone Soulblighter *did* want to work with--Shiver, the famous battle sorcerer. That's why Myrdred referred to "strange bedfellows;" he knew there would never have been an overt Damas-Ravanna alliance. When he addressed her by her true name, Ravanna knew he had the power to blow her cover, and so she had to try to kill Myrdred for fear Soulblighter would find out she was an impostor.
--SiliconDream
