The human man from Channelwood is one of the many strange mysteries embedded in the worlds of Myst. He apparently knew Atrus' language, but whether that language was D'ni or a surface language has never been clarified.
The man communicated to Atrus a story of the death of the rest of the humans on the island, shortly after which, with a brief, cryptic departing statement to Atrus ("We had expected you to come sooner"), he walked off the end of a walkway in the treetops and fell to his death on the boardwalks below.
The monkey-like inhabitants of the Age buried him in a funeral-pyre fashion after his fall.
It is speculated that somehow, this man was a D'ni survivor, or that there was an ancient prophecy regarding the arrival of someone such as Atrus, but the exact meaning of his comment is not currently known.