Multiple people have been invited to the star-chamber located in The Constant, and the invitation is more of a poem then a guide.
The paper says :

Follow the black moonstone path, be careful so you do not face the bees wrath.
Up the floating star staircase you'll go, beware of the sprinkled snow on it though.
There is no door, just walk right in, and you shall meet the star god within.
A portal to the Constant is what you also need.

You've seen a portal to the Constant somewhere before.
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Your here. With the others. You need to find a moonstone path as it says.