I like to believe GF, guardian forces are made from mascots, and are given the strengths that someone as powerfull as squall believes they get, in a sense eternalizing the warrior in the form of a guardian. I like the time loop concept that riona is ultimecia, even if dismissed. I believe greiver was made from the ring rinoa gets from squall, and since the gf is squalls essence, it's why it fed of his memory, and caused rinoa to forget him, while she became ultimecia, and obsessed with compressing time to get something she knew she wanted. she couldn't remember what, and ended up being the one to kill squall. with all the twists in the story line, that would fit right in, and leaves conclusion