I already pointed it out in his
other thread, and I wasn't the only one to point it out either.
Wizards and divine spellcasters must prepare their spells in advance. During preparation, the character chooses which spells to prepare with metamagic feats (and thus which ones take up higher-level spell slots than normal).
Sorcerers and bards choose spells as they cast them. They can choose when they cast their spells whether to apply their metamagic feats to improve them. As with other spellcasters, the improved spell uses up a higher-level spell slot.
"
when they cast" The rules are really quite blunt about it, it happens
when you cast your spell, not before, not after, but
when.
At worst it all occurs simultaneously, in which case it still works. The only way the feat won't work is if the energy description is changed AFTER I start to cast. And if that's the case, I REALLY want to know, because there are some really evil rules abuse I can think of.
Still wrong... in order for the spell to be cast spontaneously via IoA it has to have the fire descriptor prior to casting the spell. Gaining the descriptor simultaneously with the casting does not grant you the ability to cast it spontaneously. In what universe is simultaneous synonymous to before?
Example:
You have an Ice spell and can only spontaneously cast fire spells... you didn't prepare your ice spell as one of your prepared spells for the day so you can't cast it... You have Energy Substitution [Fire], but since you didn't prepare the spell and it's not fire already, you can't apply the metamagic to the spell.
Even if you had prepared the spell that day and even if you did so with Energy Sub[fire] applied to it you would still be limited to casting that spell however many times you prepared it since Energy Sub does not change the actual spell. You have 1 casting of a fire version of your ice spell, you didn't change the spell itself into a fire spell.
Sure you could theoretically cast that one prepared casting spontaneously... but what would be the point in that? you would either be logical and use the spell normally, or be illogical and sacrifice another prepared spell to wastefully cast your prepared ice[fire] spell spontaneously effectively burning 2 prepared spells in on one spell.
Infact what your trying to do is an example of a catch22... The only way you can cast your ice spell spontaneously with IoA is to spontaneously turn it into a fire spell, but the only way to turn it into a fire spell spontaneously requires you to already be able to cast it spontaneously, thus removing the need to modify it to begin with. So basically a catch22, the requirements to fulfil your desired intent negate it and prevent it from happening.