The stars are right

[Captain Obvious]

Am I going abso-frickin-lutely insane, or is there a Limitation officially published somewhere to the effect that a power limited thusly can't be used except [once a month/once a season/once a year/once in a blue moon] when conditions are just so? I just went through 5ER (paying special attention to the Limited Power Limitation) and Fantasy Hero's Magic chapter looking for this thing (which I'm sure I've seen before), but I can't find it.

HELP ME!

[Curufea]

It could be in the FHG or FHG2. But I definitely remember reading about limited time for a power. I thought it was FH. And there was definitely and option for "when the stars are right".

Is there a consolidated index available online?

[OddHat]

I think you're looking for Window of Opportunity. Hero Designer has it. Not sure which book it's in.

[aylwin13]

According to HD, it's in Fantasy Hero, page 136.