City of Endarkened

So every Shadowhunter has to go to idris because Sebastion is attacking all the institutes. While there in idris clary and izzy gets captured by sebastion and are forced to drink from the infernal cup. The lightwoods, jace, Jocelyn, Luke and Magnus start to look for them but after searching for years and still nothing they stop. Until idris gets attacked and everyone has to go back and someone or should I say some people are waiting for them.