Quote Originally Posted by Psyren View Post
That doesn't change the fact that the feat is a metamagic feat. It simply does not apply when you're not casting or preparing it, making it meaningless outside of those contexts.

(Edit: What Eisfalken said)
This is easier to understand when you parse how the feat applies to the spell.

Q: Is a sanctum endure elements spell a 0-level, 1st-level, or 2nd-level spell?
A: It is a 1st-level spell. The base spell, endure elements, is 1st level, and sanctum does not change which spell slot it goes into (i.e a 1st-level slot). RAW says so right there in Complete Arcane.

Q: When you cast sanctum endure elements, is it a 0-level, 1st-level, or 2nd-level spell?
A: It is a 1st-level spell. For purposes of spell level, such as saving throw DC and other statistics, it is either counted as a 0-level or 2nd-level spell, but only at the time you cast it and not an instant beforehand. The spell does a quick check of the conditions where it is cast:
1. Spell is cast outside of the sanctum = -1 spell level applied when spell is cast. This in no way allows you to use a lower-level spell slot to cast it, even spontaneously. A sorcerer casting this spell still takes a full-round action to do it, and burns off a 1st-level spell slot. However, if he were required to make a saving throw against the spell for some reason, he makes the save against a 0-level spell, not a 1st-level spell.
2. Spell is cast inside sanctum = +1 spell level applied when spell is cast. As above, if you were forced to save against such a spell, you save against a 2nd-level spell.

The feat isn't written badly; there's just a lot of people here don't seem to know how Sanctum actually works (or they are being deliberate about that, so they can cheat the game somehow). It doesn't actually modify the spell level at all until the very instant you cast it. That's because it has to do a check for the location it is cast in before determining effect. The spell never counts as 0-level, no more than it counts as 2nd-level. It's a 1st-level spell until it fires off, then it is altered into something else at that moment. By then, however, it is too late: you burned a 1st-level slot just to get it off in the first place, and it most certainly occupies a 1st-level page in the book, not 0-level.