First off a lot of good fluff in here. Good job Vorpal.
Confusingly worded. How about:Redo: You may reroll any roll you made in the same round, every 5 rounds. Your final reroll must be kept, even if it is worse than.
You may, as a free action, reroll any roll you made in this round. The reroll value must be kept, even if it is worse then the original roll. You may use this ability once every five rounds.
Nice and flavorful.Regression: Despite your appearance, a day with Praeter is like taking a dip in the fountain of youth. For all intended purposes you revert to the Age Category of Adulthood, gaining a +1 to your physical stats per age category you regressed (minimum +1). Your mental stats are unaffected. You do not age a second while bound to Praeter, nor can you be magically aged.
Looks good.Start Over: Each time you make your pact you must decide whether to accept or decline a special offer by Praeter. If you accept he will turn back time for your body and soul if you should die while bound. The exact time of the binding on the next day you awake with no memory of your time bound, but in the exact same shape directly before the binding. Anything taken from you is still gone, but physically and mentally you are exactly the same. However, upon awakening you must complete the ritual again and he automatically gains full control over you when he wishes. The limits to what he can make you do is the same as Dominate, so that you will not harm yourself or do something in direct opposition to your alignment such as killing a friend. Praeter only takes direct control if you would attempt to go against his inclinations, though has the ability whenever he likes.
While the individual abilities looks good, this doesn't seem to have enough of a kick to be a level 7 vestige. I'd probably drop it down to a level 6.