Re: Power fueled by rare energy
The -5% is for not being able to use your normal FP in addition to the ER to power the ability.
If you had a 10-point ER and a 10-point FP pool, powering from one or the other would really be a feature; powering from either gives you 20 points to work with, and is relatively advantageous. For that matter, if the point level is such that you have a large ER, say 100 points, then not being able to use those last 10 is barely a nuisance most of the time. -5% might well be generous in many circumstances.
And of course, if a power doesn't Cost FP, it doesn't need the ER at all. I'd allow the -5% only in conjunction with Costs FP. Likely these two are added into the Power Modifier for the setting so that all abilities must have those disadvantages to make sure the magic has the desired feel.
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