The Excalibur is one of two prototype ships built by the Interstellar Alliance. The other ship was the Victory. The two ships were intended to be the first in a fleet of Victory class heavy destroyer vessels.
Excalibur features energy and particle beam weapons. The forward guns operate at two main power levels. Level One provides beams with slightly more strength than a standard White Star. The Level Two energy weapon was copied from Vorlon technology and not fully understood. The discharge originates from three emitters mounted on large "fin" structures at the ship's stern; the beams converge just forward of the bow into a single ravening blast that can destroy nearly anything in its path. Firing this titanic weapon drains all the ship's power and the "Excalibur" is unable to maneuver, fire weapons or use long-range scanners for approximately one minute afterward.
The Interstellar Alliance turned the Excalibur into a research ship, loaning it to Earthforce in the process. Commissioned as EAS Excalibur, Captain Matthew Gideon took command of the ship, and with his crew set out to find a cure to the plague before the plague activated five years later. The beginning of this quest to discover a cure was shown on the Crusade television series. However, only 13 episodes were shown - creative differences between the series creator and the TNT network led to the show being cancelled. The Sci-Fi channel had expressed interest in continuing the show, but did not have the budget to do so.
At some point within the next five years, the Excalibur succeeded in finding a cure, and was able to destroy the plague. The ship's future has not been documented. It remains to be seen if the ship will make any future television or movie appearances.