In my understanding, you seems like show some information only once, right?
I don't recommend this kind of method because it forces user to load saved files or find for introduction which has spoiler like wiki, for only one mistake, carelessness, or maybe their short memories.
but anyway, what is your purpose, to do this, you can simply use conditional link
To the right is a <<if $mirror ==1>>mirror<<else>>[[mirror|hosp-mirror][$mirror to 1]]<</if>> reflecting the blue room. It's reflection showing something glowing on a bed.
but with historical undo button on sidebar, it will undo the variable values so link will be back.
to avoid this, you can destroy side bar or historical undo/redo button.