The Frontier is featured in X-COM Interceptor.
It is a globular cluster approximately 100 light years from Earth. The probe that found it in October 27, 2065 reported that there are dozens of star systems nearby, nearly all of them supporting planets with incredible mineral wealth and even traces of Elerium. The first corporate outposts were established in November 2066 using Elerium-powered interstellar hyperdrives. Because some corporate leaders expressed fear at the thought of expanding to the stars might result in another encounter with hostile aliens, a joint meeting of business leaders and the world governments is held. It is decided that a defensive force should be established on the Frontier, standing ready to deal with any threat that might arise.
F. Denman Williams II, successor to the X-COM corporation's former leader, agreed to turn over limited control of X-COM to the government so that defensive bases can be established in the Frontier. Meanwhile, to avoid stretching the organization's resources too thin, Williams signed an agreement with a private security firm to take over the X-COM bases on the Moon and Mars. This firm, operating under the name of Marsec, quickly gained renown for its ability to keep the local peace.
The first X-COM base in the Frontier became operational on January 1st 2067. X-COM bases operating in the Frontier were funded by corporate outposts throughout the sector. It was later discovered that the aliens have begun operating as well, setting up outposts, bases and mining installations of their own. Their forces comprised mainly of alien species known from the First Alien War but there were previously unknown species too. Also, one of the black holes in the Frontier functioned as the entrance to the alien homeworld. After the defeat of the aliens, the Frontier came under total X-COM control.