Polyphon Antiri
Once Mikhail's friend, and one of the very few to call the amiable mask a mask
Polyphon and Mikhail were friends when they were younger, and she hates him now. She had fallen out with someone, the sort of quarrel a set of friends takes sides over, and Mikhail moved to defend her by putting a vicious rumor about the other party into circulation. It did what he built it to do: the person came out of it painted as something appalling. Then it went further than that. If they were so bad, the reasoning ran, Polyphon had known it all along and had said nothing, and the friends turned on her instead. She was left outside every circle she had.
She is one of very few people ever to have named the thing in him plainly, the vindictive and petty disposition under the amiable mask, and she came by the reading honestly.
It sits among his worst regrets. He may have been in love with her before any of it.