I've been looking for spells that effectively lower the dragons chance to resisit, and found a few useful ones....
Weaken resistence which would lower his SR by 12 points...
Greater Enhance Magical Flow, gives the caster +2 to his DC checks, I believe this spell is stackable on itself, I see no where in the spell description that its not.. however that wo0uld be really powerful so I am prolly wrong, anyone know???
Soul Bend, lowers will checks by 7, I believe this can be cumulative also, but I need to lower the fort saves so i can disenegrate! hehehee.
Bestow Curse, gives -4 to all saving throws, attack rolls, ability checks, and skill checks (would be pretty useful) Perhaps the DM would let me fashion my own curse to where instead of getting -4 to attack rolls, avility checks, and skill checks, it would ONLY decrease the saving throws by a larger number. since I am taking off three other -4's, I was thinken add a neg 1 for every two negs takin away, so add a neg 6 to saving throws as well, bringing it to -10.. This prolly still wouldn't keep it balanced with the orignal curse though, so perhaps just -8.
Gimme thoughts on these and any others u come across