The OP didn't say anything in his OP about time limitations, just if there was "any spell that could damage it". *shrug* Isn't there an epic feat somewhere that would allow to to speed up that time? If not, go invisible while casting it. You won't go visible again until it spell goes off. Or go Greater Invisibility. It doesn't have Scent, or Blind-fight, or anything of a sensory nature. heck, if you're paranoid about it, Silent Spell the Major Creation and go invisible.