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Reading scroll of danger will make things worse. Even the first cavernous level has a higher DL than any of the items that would be helpful.

Going from level 21 to 24 could require something like...

You'd also need trees, which aren't available there until level 22.

First cavernous level in UC would probably be the most practical. Climbing set, ring of djinni summoning, and wand of wishing (yeah, right) are all possibilities there. Farming wilderness encounters...