Thunder Force IV is a shoot'em up game released by Technosoft in 1992, for the Megadrive console. Is also known as Lightening Force - Quest For The Darkstar.
Galactic Year 892. In the last two years the Federation collected information about the existence of the subsystem "Vios", which could be called the heart of Khaos. Considering this, the Galactic Federation mobilizes all of its power and embarks on a search for this new menace.
However, the Vios forces had used this time to strengthen theirselves, creating new weapons one after another which were unlike anything seen in the past. As a result all of the Federation's operations failed.
The Federation Army, with no time to spare, decided to inject all of their efforts in the development of the next generation of their ultra-high performance fighter aircraft which was under development, the Fire LEO-04 "Rynex".