When exactly do extra life tokens fade?
Extra life tokens fade at the end of the turn, just after the players' turn ends and just before the Shadows' turn begins.
Does "Time Dancer" allow the player to re-roll a complete roll, or just one die?
A complete roll. So, if the player makes a roll with 5 dice and then invokes the "Time Dancer" ability, the player gets to make the roll all over again with all 5 dice.
Do the piles have to be evenly constructed for "A Shattering of Souls"?
No. The player can divide his avatar's soulshards into pile A and pile B however he wishes. In fact, one pile can be totally empty. Once the piles are made, the player rolls 1d6 to determine which pile is destroyed (e.g., 1-3 destroys pile A and 4-6 destroys pile B).
When an avatar gains a creature ability, what do you use as the avatar's power for power rolls?
An excellent question! (And something for the rule book in the next printing!) Use 3 as the avatar's power for ability power rolls.