Well, you can always use secret tags.
Anyway, that is a very difficult section and I can't really help you with it for a few days because I don't have TCB on this computer. But you do go about it the same way as the other sections, it's just more difficult. If I remember correctly (even though I made the room I never remember exactly how to do that part)...
Click here to view the secret text
×You need to push the mirror in from one entrance, then go back and continue from a 2nd entrance, then leave through the third.
Game on,
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"
He who is certain he knows the ending of things when he is only beginning them is either extremely wise or extremely foolish; no matter which is true, he is certainly an
unhappy man, for he has put a knife in the heart of wonder."
-- Tad Williams