Every good story needs twist and turns, as well as, betrayal and intrigue. One reason, I made 3 of the major characters triplets is because one could pretend to be the other. In this case, Thurn can pretend to be Tharn. It is a bit cliche’d but only Galdermung catches on when he realizes his old friend is only using his left hand and Tharn was a rightie. Contrived? maybe a little…but its context may help the reader see past the not-so-subtle reuse.
This is a conceptual scene when Galdermung confront Thurn and the two battle.