Yeah, I think Bob tells Harry something along the lines of "Listen, Little Chicago had a major flaw, it should have burned you out when you used it, but somehow it's fixed now."


And that stuff with Lash was all stuff Harry was at least aware of.

That is, Lash has the capability to add Hellfire to Harry's spells as he casts them. She doesn't (that we've seen) have the capability to cast fire spells without Harry realizing.