[drewal]

I would not be surprised if it differs depending upon the patch-state of a game, but with my game's state, incendiary Cloud, Grease and Web definetly bypass MR - this is how I am killing the first incarnation of improved Irenicus - immobilizing area of effect plus icendiary cloud.

At least one of the three insect spells seem to bypass MR as well since the Fallen Planetar can hit improved Irenicus with insects.

I do not now about Glitterdust or Sphere of Chaos - I'll try 'em out next.

I will double check cloud kill and death fog as well - though I am pretty sure I have damaged the third incarnation of irenicus with at least one of these, using the same web-cloud tactic - though I did cast two incendiary clouds a death fog and a cloud kill on him at once so I might have misread the scrolling text.