First of all...Welcome to IronWorks Ladie!
As Rodimus mentioned, you shouldn't have to lure the demon anywhere. I simply summoned a bunch of Skeleton Warriors and Fire Elementals and hasted everyone. Released the demon, sent the summoned monsters into melee with the demon and proceeded to pound him with missile weapons, a couple of Lower Resistance spells, then magic missiles and chromatic orbs.
You also should have found a series of notes throughout the level that give you a clue as to how to beat the demon if you are lower level. He is susceptible to different elements depending on what his current incarnation is (he switches between fire, ice, normal, and slime). Each incarnation is susceptible to something. For instance, in ice form...he is susceptible to fire. Flame Arrow spell works wonders! Hope that helps!
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Now where did I leave that doughnut?!