Actor: Robyn Miller (Myst), Brian Wrench (Revelation)
Race: 1/2 Rivenese, 1/8 D'ni, 3/8 Human
When Sirrus was 8, his great-grandmother, Ti'ana, died. Atrus, unable to properly cope with the loss of his beloved grandmother, took to burying himself in his work at the expense of spending time with Sirrus and Achenar. Sirrus, who by this time already had an over-developed sense of pride and ego, felt ignored and unwanted as a result of this, and it is believed that this was one of the key events that pushed him to become the egotistical maniac he grew up to be.
It is believed, based on the evidence in his room in the Stoneship Age, that Sirrus and Achenar were in cahoots with the Black Pirates from the Mechanical Age. The plot of the defunct comic book series further re-enforces this speculation, but we presently have no information on their cooperation or the scope of any joint operations they might have undertaken. It seems, though, that cooperation was not one of Sirrus and Achenar's strong suits, as their plans would often quickly degenerate into bickering and debate.
Sirrus appears to have been the mastermind of a plot to take over the Ages of Myst. Until recently, the plot was thought to have focused solely on gaining access to the two Prison Books in the Myst Library, which the boys had been instructed never to use. However, recent information from Myst IV: Revelation has revealed that the plot was much more insidious than originally believed. Sirrus had plotted to capture his father after first baiting him to a controlled location (K'veer) by using Catherine as the bait. He and Achenar would then take him to Serenia, use a Memory Exchange Chair they had constructed in the old Memory Chamber to extract Atrus' memories from his body, and insert Sirrus'. Presumably, through the use of Atrus' body under Sirrus' control, they would be able to seize control of the Ages of Myst much more easily. It can only be assumed that the plan was to kill Atrus after Sirrus returned to his own body to continue the domination of the Ages.
However, the plan was side-tracked by Sirrus and Achenar's greed, and each became trapped in one of the two Prison Ages on Myst Island, which were for the first time left unguarded by their parents.
Sirrus spent nearly twenty years on the Age of Spire, his hatred for his parents growing more intense with each passing year. Despite his numerous accomplishments during his confinement, his sole objective was to find the Myst Linking Book which he was convinced his father had somehow left behind, however unintentionally. Eventually, Atrus and Catherine began to think better of their decision to leave their sons trapped, and access to Tomahna was created through a secure linking chamber made of nara, the hardest of D'ni stones.
Sirrus, through the application of molecular physics, was able to break through the secure chamber and escape his prison. Now determined to learn how to Write, he planned to capture Yeesha (toward whom he harbored intense jealousy, thinking that his parents cared for her much more than he and Achenar), transfer his consciousness into her body using the Memory Exchange Chair on Serenia, and pretend to be Yeesha as Atrus taught "her" the Art. Once fully educated, he would transfer his mind back into his own body, kill his parents, and go on to rule over as many worlds as he wished.
Fortunately, his plan never came to fruition. Through another fortuitous appearance of the Stranger, he was foiled with Achenar's assistance, saving Yeesha and killing Sirrus in the process.