The Narsil is an Excalibur-Type Chemical Laser Tower developed from information recieved from captured Belkan Scientists. Like Excalibur it's range with the help of mirrors is anywhere around the globe.
Narsil is primarilly used as an Anti-Missile system but also has Anti-Fighter and Anti-Ship capabilities.
During construction, Narsil proved to be very finicky. Some of the system's parts had to be put in a certain way or it wouldn't work, and entire sections of the superstructure had to be taken apart to fix small bits of the weapon before construction could continue. Many billions of dollars were put in to construct the Tower before it was finally completed.