City of sweet revenge

When clary, Jace and the others returned from Edom they expected their lives to return to normal. Clary would finish her training, Jocelyn and Luke would get married, Jace and Isabelle would continue being hot and they would live happily ever after. This dream was exactly that, a dream. Mysterious threats, deaths and disappearances are occurring, and the New York institute cannot ignore it any longer.
They think Sebastian is dead. They were there, he died right before their eyes. But they haven't yet realised that Sebastian's soul never died. Jonathan's did. And they weren't the only ones to get favours from Asmoedus.
With a few new faces added to the mix, a couple of relationship problems and an extra serve of revenge and betrayal, this is a story you won't want to miss.
ERCHOMAI
I AM COMING

( just to get you all Excited, I have added an extra bit!)

The shadowhunters believe that they alone protect this planet, they laugh at the mundanes who live in their sheltered world, but what if they too are missing something, or as it might be, someone? Maybe some of the stories we know as fiction are actually true, we just can't see it? And the shadowhunters can't see it either. But now they need help.

A secret of the clave, lost in time and known to only one person who still breathes, is resurfacing. The wards are weakening and more demons get through to our universe, but that is common knowledge. The clave claims that the demons are gaining strength and that is the cause. But they're wrong. The wards were never completed, there is a final piece that was never perfected, wasn't ready to be added to the earth's protection and now it can destroy everything.