When the Mentor Aspect is the target of Unlock the Gates of Deepest Power, what happens?
Shifting Memory of Ages draws two Major Powers, gains them both, and forgets nothing. If they meet the threshold requirements, they can play one of the new Power Cards – since the identity of "the Major Power" is ambiguous, Shifting Memory of Ages chooses which one is being referred to.
While this tends to be pretty obvious when the cost is paying Energy, it's less clear if the cost is performing some other effect, like discarding a card or removing Presence.
If you choose to pay with Energy, Begin a Dance of Decades lets you pay any amount of Energy – even more than the amount you'd normally have to pay. This may be advantageous if you want reduce the time it will spend impending. The impending card will then come into play on a future turn, like impending cards normally do. It won't automatically gain all elemental thresholds on that future turn, and it won't have an energy discount, since those effects of Unlock the Gates of Deepest Power expire when Time Passes this turn. Tags: Forgetting, Unlock the Gates of Deepest Power, Rhythmic Power Builds to a Cataclysmic Crescendo (Dances Up Earthquakes), Begin a Dance of Decades (Dances Up Earthquakes), 1 more...