Suppose I play a Slow Power card that requires a Sacred Site.
But I miscalculated and in the Slow Phase I have no Sacred Sites any longer.
Can I still benefit from the elements infused (sorry Gloomhaven) of that card for any Slow Innate Power?
If you paid the energy for a power card, you always gain the elements even if the board state changes and you can no longer use the power card for its text effects:
rules pg. 8 wrote:
If a player discovers they do not want to use a Power's text effect (or cannot use it), they may choose to skip it entirely. Sometimes, a Power Card will be worth playing purely for its Elements.
rules pg. 16 wrote:
You gain Elements the moment you pay for a Power Card, regardless of whether the Power is Fast or Slow, and they go away as soon as it leaves play (usually during Time Passes).