I could see Jonathan Groff in this role. I think he could play someone with an expansive personality, quite pleasant and magnanimous if you're on his good side, but with a dangerous edge. I'm thinking of his performance of "You'll Be Back" in Hamilton: it's this bouncy, sort of goofy-sounding Brit-pop song, and then, oh, by the way, "I will kill your friends and family ...". There's suddenly this huge menace in the words and it sort of creeps into his tone, but he carries on singing in this really cheerful, albeit increasingly deranged-sounding way. I can see that kind of edge working really well in his early scenes with Luthien, where he presents himself as a benevolent rescuer ... and then imprisons her for himself.