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Originally Posted by
chemonz
Save DC for all spells = 10 + Spell level + ability bonus (Int for wizards, Cha for Sorcs) + any spell focus feats or items for the school of spell you are casting.
So a lvl 14 Sorc casting charm monster with a cha of 34 (+12 bonus) would have a dc of 10+4+12 = 26, if he is holding an enchantment focus item his DC would be 27.
Heighten spell is a metmagic feat that, when active, increases the spell level of any spell to the highest spell level the character can cast. So it works on all but the highest level spells. So the same spell cast by the same sorc would be dc = 10+7+12 = 29, so in this case it would raise dc by 3.
I always find an example helps to explain the somewhat complicated way spell dc calculation works. Scorching ray is nice because there is no save for 1/2 damage like there is for fireball or cone of cold, you just need to hit the target which usually isn't hard unless the target is moving around quite a bit.