Alkion was the 2nd moon of Arsia Prime, and was the site of Project Specter.
Alkion was the site of the REotH's Project Specter, a prototype weapons system that turned Alkion into the desolate moon it is.
The Sites of Specter 1, Specter 2, Specter 3, and Ghost Base Alpha, and Ghost Base Omicron are still on the moon, but all other bases were destroyed by the Ghost Array of Project Specter.
Behind the scenes
The Ghost Array is based of the Mass Shadow Generator, but not as devastating.