Myst-Vearn is one of the main antagonists, and one of the strongest in the series as well. He is the very definition of a shadow, completely silent, even if present. He is so quiet and reserved that it is infamously said he only speaks once each several years, an infamy backed up by being such a highly spectral entity. He will only speak the bare minimum and only if he deems it absolutely necessary to do so, otherwise he tends to act through gestures. 

Although he does not speak a large amount through the majority of the series, he does appear throughout until his major fight later on. So I would like to cast him now even if the lines are minimal until then.

I would like his voice to be a bit quieter and maybe with a bit of a hiss. Something unnerving sounding but since he is fairly quiet, not over the top either. If you have another interpretation of him though I'm very open to hearing other options.