Okay, it's this substance... creature? It's sort of like a mineral but it's sort of alive. Long story. The short part is that processed lyrium is used in magic, but it can have bad side effects if you get too much exposure or handle it wrong.

The Venatori were experimenting on those of us with anchor shards, using lyrium. It wasn't good. At all. But... no lasting effects, I got a clean bill of health from the healers. Or as clean as I started with.

[Her voice is admirably steady, but muted. She's trying not to shut Sarah out, but it's clearly also something it's hard to dig into deeply.]