After destroying so many of hte creatures, Natsu had started to learn instinctively where they were the weakest, his kills growing startlingly more efficient despite the numbers. Which was why he had even stopped screaming and calling out at this point.

The moment he burst into the room where the voices had been, Natsu realized he was close. But since his target was actually below him now, he quickly summoned Lucy's gift, the gauntlet and proceeded to tear up the ground fighting the very earth and stone and ice itself as he tunneled downwards, reaching the coffin and not stopping until it was sitting in a dug out crater.