The Eltreum (ヱルトリウム) is a high-tech spacecraft which was used to reach the center of the galaxy for the final battle against the Space Monsters on May 22, 2048. It is the largest manned spacecraft ever built by mankind. Like the Exelion, it was piloted by Tatsumi Tashiro. Unlike its predecessors, which used more conventional propulsion methods, the Eltreum is propelled by the power of pure mathematics and controlled by ESP-enabled porpoises.
In 14,282, the remains of the Eltreum are discovered once the Red Milky Way dissipates. The front of the ship appears to have decayed over time for an unknown reason, but the rest of it, being built from a man-made
element that could only be destroyed by an exact opposite element, is unchanged.
The Eltreum is a large 70km long triangular craft. Since the only episode of the original series it appears in is in greyscale, its true color was unknown until its brief appearance in Diebuster, where it was confirmed to be white.