The Humbles
Each of them have souls as black as soot. Cowards or avowed criminals, all of them follow the philosophy. Their blackened hearts may serve my purpose yet, and may just save this town from certain destruction. From them I will choose those that will give up their lives to keep the balance of this strange town, and in doing so, both the miracle of the Polyhedron and the miracle of the Town can co-exist.
She appeared before me in a dream...
...looking scared and miserable. She said, "They persecute me, they hunt me, they try to track me down. They are so close to capturing me that I had to change my hideout four times in a single day. I am covering up here, at the brink of the town, where they won't find me so easily. From the windows I see two bonfires being lit are they trying to smoke me out? Are they going to put a watcher atop the ruined stairway surrounded by columns?"

I know you are interested in pairs, oppositions, and other meaningful similarities, so let me remind you of something.

The first pair should be read as follows: if the udurgh Isidor spoke of is the town, then the Polyhedron is the sacrifice.

There is no other way, since the two are correspondent to each other.

Crush the Polyhedron—and rivers of blood will flow, the underground ichor emerging from within the hollow rod on which the Tower stood.

The second pair means: if Aglaya is the sacrifice, then Simon is the udurgh. In this case you have no other choice but to protect the Polyhedron.

I am staying in the left wing of the Termitary, come and see me if you please. My plan is the only one that is feasible.

Nothing will have to die.

Button of the Changeling, text states