A Life Stone is an integral part of the Memory Chamber in Serenia and helps sustain it. Without it, the Memory Chamber would collapse and wither (as seen in Myst IV: Revelation's ending). Achenar steals the Life Stone on Serenia to stop the Memory Chamber from working, just long enough to thwart Sirrus's plans to take over Yeesha's body. However, he does not do so in time and the chamber starts to collapse while The Stranger reassembles Yeesha's memories. Achenar sacrifices himself by placing the Life Stone on the core of the Memory Chamber itself, releasing deadly toxins but stopping the collapse.