By 10 rounds, you mean 1 round, right? Assuming we are talking about metamagic use (not even metamagic ABUSE!).
Also, Gnomish Phantasmal Killa has a DC of ~14+7 (int) + 1 (racial) +1 (spell focus, you know...for Archmage)= 23
+12 fort save is a save on 12+, with a 19+ needed on the will...