Because you get the note from Kandin in Butcherblock from turning in Cazic's Skin. You have to turn this note in to Dargon to spawn the version of Arantir who will accept all 3 staves (Gabstik, Blue Crystal, Gnarled).
The Mistletoe powder simply gives you the staff of Gabstik.
And I've seen the "Cazic Skin MQ" selling for 500K, just to piggyback off of a wizard who is already spawning his epic mob.
[You must be logged in to view images. Log in or Register.]