“I know what you were thinking,” Magnus said. “But there was no re. That smell is
hellmist—it’s a sort of enchanted demonic smoke. It mutes the eects of certain kinds of magic.”
“Demonic mist? Then there was—”
“An attack on the Institute. Yes. Earlier this afternoon. Forsaken—probably a few dozen
— City of Glass by Cassandra Clare
Chapter 2: The Demon Towers of Alicante
Hellmist? What is this nonsense? Why are we are now after two books hearing about Hellmist when our cast of idiots have encountered two Greater demons and hordes of lesser demons? No, Clare pulled this straight out of her ass and she’s not kidding anyone!
Also, this makes no sense that Forsaken are using demonic smoke when they are not themselves demonic. According to Shadowhunters Wikia Foresakens are defined as:
Forsaken are beings who were once mundanes who have gone insane upon receiving powerful runes they are unable to handle. They cannot be returned to humans and have no knowledge of their previous existence. They come in different forms.
Do you see any demons mentioned in this? The only way I can logically see Forsaken using Hellmist is if Valentine did it by proxy. Yet, I have yet to see any evidence that Valentine is even that powerful? Honestly, The Clave could have taken him down easily if they weren’t a bunch bungling dunderheads!
No, Clare pulled this out of her ass so she can look cool and was too lazy to actually try to make it work.