Do you have "Create Portal" and "Teleport" yet? That makes it easy; to set a portal on the "Brimloch Roon" side of the Spire and then slide down the cliff. You can then teleport over to it.
Other than that, it's back through the spire.
However, there's a couple of tricks to make it a lot easier. I'll see if I can find some of the older posts and bump them up.
-Sazerac