"Immortal and invulnerable." Phillip isn't keen to go into the specifics of why he is both of those things- he's slowly, slowly getting there, but there's work to be done yet. Still, if Shido presses again he'll answer. "And I can teleport so the chance of you cornering me is pretty low too." Not to mention being able to straight up murder him, but most people don't seem to like hearing that even when he does share.