Achenar's altar is a mechanized offering table located on the third level of Channelwood, just across from Achenar's bedroom on that Age. When activated, the "jaws" of the altar snap shut, and the material placed on it as an offering is dropped into a chamber below.
The altar also has an imager built into it, which activates whenever someone enters the temple room. Achenar was able to choose from one of four recorded messages from another imager device in his bedroom. Three of these appear to be in the language of the Channelwood natives, while the fourth was recorded over by Sirrus, who left a message for his brother instructing him on how to sabotage Atrus' Myst Linking Book.
- The recording with the close-up of Achenar's mouth is actually the phrase "Rush Limbaugh understands" played backwards.