Channelwood Man
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.