The Sphere is the main antagonist from Super Aleste.
In the year 2048, a mysterious sphere of large proportions comes from space and falls on Earth. Before anyone can investigate the object, it starts attacking Earth and drain the surface's energy to expand itself, creating lines similar to the Nazca drawings wherever it passes. Earth's military fights off the invading force but is unable to attack the Sphere directly due to it's defensive systems. Because of this, the military begins construction of a new spaceship, the Super Aleste, which succeeds the original Aleste fighter and is tasked to fly into the Sphere and destroy it.
In the American version of the game, the Super Aleste is piloted by an unnamed pilot, who dives into the Sphere and destroy it's heart. This causes the Sphere to self-destruct, with the pilot barely making out of it and surviving.
The Japanese version of the game had more backstory, explaining more about the Sphere's nature. In this version the Super Aleste is piloted by Raz, being aided by a mysterious alien girl named Thi who apparently was a captive inside the Sphere and knows it's true purpose. As they fly inside the Sphere and destroy the heart, Thi emerges from the wrecked Super Aleste and flies off towards the Sphere. Upon interacting with it and releasing the other intelligent beings which were trapped inside, the Sphere turns into a ball of light and flies back into space.