"Well, I'll be damned!"
I BELIEVE YOU ALREADY ARE.
The second speaker is obviously Death, but the first speaker is Astfgl, the Demon King, chasing after Rincewind and Eric, in
Faust Eric.
I listened to the audiobook for this many, many times, told by the inimitable Stephen. I've just about memorised the whole book.
Esmeralda Weatherwax ==> XXXX
(Aha! You thought you stumped me with 'X'!)