If I had one level of Darkfire Adept, it gives me the ability "A darkfire adept gains Sacred Summons as a bonus feat at 1st level, as if she had an evil aura (regardless of her actual alignment)."
Evil alignment? If I actually was evil, and picked up Summon Evil Monster, what about the other axis? Can I summon Lawful Evil monsters as a standard? Neutral Evil? Any evil?
You can summon creatures whose alignment subtype(s) exactly match your aura as a standard action. That means you can summon monsters that only have the evil subtype like daemons. You can't summon demons or devils as a standard action because they have the chaotic or lawful subtypes.
With the Summon Evil Monster feat though, it says "Special: If you possess the Sacred Summons feat, you can apply it to a creature on this list whose alignment (as opposed to its subtype or subtypes) matches your aura."
There aren't any creatures with just "Evil" though, it doesn't state the other axis.
Should I just assume that Evil means Neutral Evil? Fiendish creatures and Daemons?
Should I just assume that Evil means Neutral Evil? Fiendish creatures and Daemons?
Yes. 'Neutral' is never in an aura, as an aura is basically just what 'is' not what isn't. You can detect Evil, or Good, but you can't detect 'Neutral' on the Good-Evil axis.
The summon evil monster feat isn't written all that well, but it is pretty clear that an aura from a NE source (which ends up just being an Evil Aura) gets monsters with an NE alignment.
Hm. A question then. If I dipped cleric to a Chaotic Evil deity, and gained a Chaotic Evil aura, I can summon Demons as a standard action. What about Neutral Evil creatures? I still can't summon them as a standard, correct? My aura isn't just evil, it's chaotic evil.
I really want to make a sorcerer that summons evil monsters, because I don't want to break the game by playing a Summoner. I may just ask the DM if I can count an Evil aura as anything evil, so I don't go with a Summoner. That seems fair, right?
It has to be an exact match on both Axis.
As to whether your proposed house rule is fair, it does make the feat more powerful. I wouldn't say it is hugely more powerful, but it is an upgrade.