Reserve feats and Circle Magic are quite the fun combination.
Acidic Splatter: 20d6 acid damage, ranged touch attack, 100 ft range.
Fiery Burst: 20d6 fire damage, Ref DC 30+casting stat mod, 30 foot range.
Etc.
I was quite curious about this actually.
Add Empower Spell, Maximize Spell, or Heighten
Spell metamagic feats to spells currently prepared
by the circle leader. Each circle bonus level counts
as one additional spell level required by the appli-
cation of a metamagic feat to a spell. The circle
leader may add one of the three listed feats to a
spell even if he does not know the feat or if the
addition of the feat would raise the spell level past
the circle leader’s normal maximum spell level
(maximum spell level 20th).
These effects last for 24 hours or until expended.
If you were preparing the spell with a specific amount of metamagic applied, I'd assume the spell would be "locked" with the bonus until you use it (as per the wizard's ability to keep spells from previous days). However, the wording of circle magic seems to be applying the metamagic as a temporary (24 hour) effect to an already prepared spell. This means you would need to create a circle EVERY 24 hours to keep your reserve feat boosted. It's a cool downtime buff that lasts 24 hours if you happen to have a bunch of guys with circle magic around, but in a normal game of "adventurers going everywhere" there isn't much opportunity for it (especially when leadership is banned or houseruled to being an offscreen support network). However, if the circle magic sticks until used, it means you could just fill a new slot each day with a level 20 spell to support a different reserve feat, then have half your spell slots as level 20 at-wills.
Yeah, the wording is vague. I go with the interpretation of "Lasts for 24 hours [caster level boost] or until expended [spells w/ metamagic]," because that follows the normal rules for spell prep.
If you are a Hathran, well, you have to take Leadership to even get in the class (3.5), or you got a free cohort anyway (3.0). Add in a follower or two who has the Ethran feat (I think minimum is you +3?) and then you can do this, if your cohort is also high enough level to lead a circle:
Cohort leads circle and you and the two followers each give the cohort your highest level slot. She uses these to boost a spell with Heighten as high as she can. Then you can immediately turn around and
lead a circle yourself, and the cohort gives you that now-heightened spell (plus whatever the followers can give you). Lots of spell levels to play with for caster level boosts, etc. It gets even better if the DM does allow the heightened spells to last more than 24 hours.
Someday I would love to see a group in my gestalt game that was composed entirely of Hathran. Sure, they'd waste 4 hours every day in Circle Magic transfers amongst each other, but their caster levels would be insane.
