Clement bore the Dragon King's mark. His demise within that labyrinth and subsequent consumption by the skeleton may well have alerted the Dragon King.
Those draconic limbs instantly illuminated Ansel's understanding... Perhaps the second Dragon Calamity wasn't solely due to his swift decimation of numerous dragons inciting their hunting instinct.
Rather... the Dragon King had sensed something through Clement as a medium!
This explained the rift's simultaneous appearance with the second dragon wave. When the rift opened and this monstrosity emerged, the grievously wounded high-tier dragons were suddenly driven into a frenzy, as if provoked.
Regrettably, the creature's presence merely stimulated their savage nature; they failed to target it specifically. Ansel, having battled the dragon hordes daily at the defensive line, knew well that their objective remained the unleashing of the Dragon King's ferocity, continuing their hunt and slaughter.