So my first thought was that Bleeder had two spikes at all times (because I thought that the Era 1 books said Kandra needed 2 spikes for thought, i.e. a Blessing). So that would mean this "Trellium" spike and a spike that gave her powers. However, I think I'm wrong about the 2 spike thing, as multiple times in SoS it's explained (by Kandra) that the first spike gives thought.
Based on the quote from the book you provided, I now think *all* of Bleeder's spikes were of this "Trellium" (or at the very least she had multiple). Here is the last part of the quote, with my emphasis as to why.
“Waxillium,” Marasi said. “We can’t identify the metal. It’s nothing we’ve ever seen before. It certainly wasn’t one of the spikes she started with. That means she removed both, and stuck one like this in instead. Where did she get them? Who gave them to her?”
Each of the underlined sections implies there is more than one "Trellium" spike (and that the characters know that).
So my conclusion is that the metal of the spike itself was granting Bleeder the detection protection from Harmony, and it has stolen a power. I also believe that "Trellium" is definitely a God metal up there with Atium and Lerasium. It is unknown as to what all this new metal can steal. I believe we've only seen Feruchemical Speed and Allomantic Steelpushes.
P.S. Hello. I'm new here. This is my first post.
