There are times when spoilers are good. very good even. Though it does depend on the person doing the reading and the nature of the spoiler
But like - The Siberian, as a character concept, this unkillable force of nature that just can't be stopped no matter what? I would be very, very, very annoyed by her existence as this 'stupid unbeatable boss that they'll find some lame gimmick for' because that kind of antagonist always annoys the fuck out of me.
That is, an antagonist whose whole schtick is that she's not just super hard to beat, but literally unstoppable is always annoying to me.
Knowing that she's a projection of Manton thanks to spoiling myself of much of the big twists of Worm makes her significantly more tolerable because her invulnerability works rather than just feeling like escalation for the sake of escalation.
Perhaps a bit YMMV, defnitely subjective but yeah, every member of S9 is just... fucking made to being narratively annoying, seems like. God they suck as antagonists.