Immortal, but Vulnerable

John stares horrifyingly at the floating ashes as they turn back to their former state, a phoenix, again. His steel sword marked the bird's death ten times, it IS immortal after all. Phoenixes live up to their legends alright, John thinks.

John swings his sword killing it for the eleventh time. But his efforts deemed hopeless. Nothing worked so far, the ashes eventually transform back.

"Sealing!" John thinks loudly. He miraculously stabbed it in the heart once again, degrading it to ashes. Quickly, he sealed the beast's remains for eternity; rendering its ability to live its thirteenth life no more.