And thus transpires the 'big reveal': Sytt was never a true yugoloth. He still worked for Charon, but as a type of daemon called a somesdaemon. When he managed to pull off a stunt which really ticked off the yugoloths (the daemons' rivals), they decided to teach him a lesson. He was bound into a yugoloth body. The spell can't be reproduced easily, though, which is why they couldn't make him a true yugoloth. That's also why he couldn't' advance in rank. The spell only lasted a certain length of time, though, and it just expired.
Note: He's actually not much more powerful than he was before. Before, his numerous items and suchwhat gave him the advantage he needed. Now, though, he's a lot more unpredictable. Not only is he free now, his superiority complex has returned and he believes himself pretty much infallible.