Thanee said:
Let's say, an Incantatrix uses the Metamagic Spell Trigger abilitity to heighten a spell cast from a wand, for example, Charm Person (1st caster level wand).
The spell level is heightened to 9th (costs 9 charges total).
Is the save DC now based on an attribute of 11 or 19 ?
Bye
Thanee
Do you know what I think? That the designers of MST didn't think about it
If I understand your question correctly, you are asking whether using MST (with any metamagic feat) also gives you a DC increase because of the minimum ability score to cast a spell of that (modified) slot level.
But... you don't need to have Int/Wis/Cha 19 to cast a 1st level spell Heightened to 9th! You need Cha 19 to cast a 9th level spell. In fact, if a caster doesn't have Cha 19 but has 9th-lv slots to use, he can still use those slots to cast metamagicked lower-level spells.
That quoted rules about wands DC is true, but it is meant only for crafting wands IMO (ok, I am not aware if and how you can make an entire wand metamagicked...).
Perhaps I am wrong, but you are asking if for example using MST to cast a Quickened Charm Person from a wand would raise the DC from 11 to 15. I don't want to sound like pedantic but I'd say no. I think we should make it work just like metamagicking a spell in your daily slots.
In the case of Heighten to 9th level, you ARE using heighten to get a +8 on the DC because of the increased level. If you rule that it also increases because of the higher ability score, you get another +4 on top, for a total +12. That would be good of course

but I think it's not meant this way.
All of this if I understand correctly what you are trying to ask...
