The Ballad of Adler Young, Canto 2.5

It's unlikely that he could have faked his own death well enough to fool the ancient magick that operates the Hall.

Ah. That's pretty air tight. The only things I can add to my previous suggestion is: could he have died and been brought back to life? Maybe he erroneously believes he's Lord Randall. Or Lord Randall can be completely removed from the equation and that suggestion can be ignored entirely.