A creepy gravitational artifact nicknamed “Mug” by stalkers for its resemblance to a human face. Scientists at Research Institute 7 have long tried to determine its composition and structure, but have not reached a consensus. Although all Mug samples look almost identical, they may actually be composed of different debris. Stalkers have noted another feature: two blinking diodes that sync to the bearer's heartbeat. Such similarity of this artifact to the Heart has spawned many tales among the Zone's inhabitants.