I can't get past this vague outline.

Hint 1 of 4:

Have you seen a similar 'vague outline' in the game previously?

Hint 2 of 4:

It was in the same place you got the Gating scroll.

Hint 3 of 4:

Don't read on until you have brought the vague outline from the Southlands of
Quendor into the Ethereal Plane.

Hint 4 of 4:

Recheck your inventory.  You should now have a phase blade.