This article deals with Achenar of the Myst series; for the star Achernar (Alpha Eridani) (sometimes spelled Achenar) see Achernar.

Achenar trapped in the Blue Book in the Myst game

Achenar (D'ni: Akehnahr/[Akenar]) is the oldest son of Atrus and Catherine.

Sirrus and Achenar were two bright young boys who grew to be confident, ambitious young men. They followed their father Atrus everywhere and had many journeys together. The two boys were very intelligent, and created many useful devices and projects to help their father in the ages he linked to. As time passed though, Atrus gave them free reign to the books all describing and linking to the fantastic ages that he had visited. However, Atrus later remarked that this was probably unwise. Unsupervised as they were, they began to change. One or both of them ended up destroying and burning all but four of the ages of Myst Island, their home island which was the gateway to many others.

Achenar was apparently mentally instable, and became obsessed with violence and death. He seems the one responsible for killing most of the inhabitants of Atrus' Ages.

In Myst, Achenar was first met INSIDE the blue book on Myst Island in Atrus's library. The book was revealed to be a type of trap or prison that Achenar claimed that his father had incarcerated him in. At first, the book has many pages missing, and when first opened without the pages, the player can not see or hear Achenar at all due to the static blocking the gateway image. When the first blue page is put into the book, Achenar is able to barely see someone looking into his blue book, he implored the player to find more blue pages which were scattered in the four remaining ages of Myst. With each page he could see out of the book more clearly. As the vision became clearer he shouted out not to pick up the red pages belonging to his brother Sirrus' red book. He slowly explained through the static which later cleared once enough pages were gathered, that he could could escape and reward the player. Like his brother, he claimed Atrus and Catherine were dead, and that his brother (Sirrus) was responsible for the destruction of the Ages. [1]

At the end of the game, the player frees Sirrus' and Achenar's father, Atrus, from his prison in K'veer. The player waits in D'ni, and when they return to the island of Myst, the red and blue books that acted as the two son's prisons have mysteriously disappeared, leaving burn marks in their place.

Later, in Myst IV: Revelation, it is discovered that the brothers are in fact not dead. With the release of this installment of the Myst franchise, curiosities and plot holes involving the brothers shall be cleared up.