How do I get here?

Hint 1 of 6:

You need a certain object to get to the Ethereal Plane.

Hint 2 of 6:

Don't continue on until you have visited the Transinfinite Planes of
Splendor.

Hint 3 of 6:

There were two items in the chest after you opened it.

Hint 4 of 6:

One was a vague outline, the other a palimpsest.

Hint 5 of 6:

Try taking each item to the woman in the Magick Shoppe in Gurth and ASKing
her about them.

Hint 6 of 6:

The palimpsest is a Scroll of Gating.