Honestly, when the new dungeon of shadows escaped the researchers, no one paid any mind. An A rank party, with the famous Jean as its leader, was sent to get it back from Samkiel's tomb, where it had holed up, and things went on as they always did.
But then, two weeks went by and the Firebolts did not come back. Then another, and the only news they got from Jean was a distressed call. The Adventurer's guild was a beehive of activity.
There was a protocol in place when an S rank sent a distress call. The guild went in force. All the parties ranked D and up were recalled from their quests and sent with a destroy order for the dungeon core or the monster that managed to take down an S rank adventurer.
Since Leander was a healer, and those were in short supply, his party was placed in a platoon with three others.