[Kransha]

The Mouth of Sauron was a human, Black Numenorean, most likely a Corsair of Umbar. He was mortal, so he was probably an Corsair of high rank offered the job by Sauron. In one of the tales (I don't remember which or where) it is mentioned that, if Sauron had won the War of the Ring, this Black Numenorean would've been given regency over the defeated western lands. In fact, Sauron would've used this ambassador to replace Saruman, ruling from a rebuilt Isengard in his stead. He was doing this purely for profit. I unfortunately do not have any quotes that can confirm these facts.