A Rivenese guard employed by Gehn to watch the entrance to Riven on the Temple Island and question them. He wears a D'ni uniform, as was of the Rivenese affiliated with Gehn. He was instructed by Gehn some D'ni language in order to be able to request any Linking Books the visitor (presumably Atrus) would carry.
He witnessed the arrival of Catherine. He managed to search her belongings for a Linking Book but found none. He must had been so surprised, that he was easily darted by the Moiety, who then took Catherine away. Nonetheless he reported this to Gehn.
When the Stranger came to Riven, he mumbled to himself in Rivenese in surprise. He saw that he carried a book (actually a Trap Book for Gehn), and attempted to request about it in D'ni. As the Stranger spoke no Rivenese or D'ni, the guard gave up and attempted to steal it from him. However, he is soon knocked out by a rebel who took the book, threw the unconscious guard over a cliff and broke the cage.
Fans refer to that character as "Cho", so named due to the first word he utters to you in Riven, in the Rivenese language. The guard is played by Vincent Ramos. Although not mentioned, it is possible that Cho is a member of the Guild of Maintainers.
The whole Cho's monologue in the introduction is in Rivenese (which, according to background information, is represented by an actual dialect of Papua New Guinea). As is the case with most of the "alien" dialogues in the game, the speech remains untranslated and as of 2015, it is still unknown to the public what Cho really said.
Of his speech, one sentence can be analysed: Cho attempts to speak D'ni to the Stranger, saying tah... tah... tahgemah b'soo rekoah. This is intentionally wrong, signifying the "broken" D'ni language Cho was able to speak. In reality he was supposed to say (to Atrus): tahgemah b'zoo ah rekor ("give me the book").
He is seen again only during the bad endings:
- When you trap yourself within the Trap Book, Gehn puts Cho in the cage of the 233rd Age and make him use the book himself, trapped within it, but as you switch places, you are "freed" inside the cage. Gehn shoots you soon after.
- When you open the Star Fissure prematurely, Gehn and Cho show up. Gehn shoots Atrus and takes his linking book, then Cho shoots you, as ordered by Gehn.