What horus heresy book did that one Defiler appear in?

I can't quite remember the book cause its been a few years, and I'm currently on the the Siege (so there's SO MANY books to remember).

But it was a space marine main character (it mightve been a primarch?) that was fighting a Daemon Engine-esque machine, and I remember in the fight, they even used the word "defiled" when describing it. I believe the fight took place in some sort of chamber?

It's been so long though I could be wrong on some of the details. Any help would be appreciated!