The Holar Tower was excavated after the Chimera invaded Iceland on July 15th, 1951, and has been the main base of the Chimera ever since. The tower seems to be a hub tower for controlling the activation of the other towers throughout the tower network. The tower was also used to create 'red' Grim strains. Advanced Hybrids were seen the most there as well, given the tower's importance and need for security.
The Holar Tower was attacked by SRPA Black Ops soldiers and Sentinels on May 17, 1953. It was a massive operation with over 75 VTOLs ferrying soldiers and dozens of F-86 Sabre jets. However, the assault is quickly beaten back with heavy casualties, forcing SRPA to retreat. Distinguished Sentinels Aaron Hawthorne and Benjamin Warner were killed by Daedalus.
After the breach of the Liberty Defense Perimeter, SRPA made a second, much more successful mission in Holar by sending in Specter Team to halt Daedalus' attempts in constructing the Prometheus Weapon.