Although this ship did exist in the
game at one time (2001), it was replaced by the newer,
chunkier and vertically-oriented Vaygr mothership-class
vessels. It is seen in the E3 2001 flyer and trailer
that were kept secret at the time.
is -- or at least was -- a mothership-sized command carrier.
One of the concept arts labels it as "Agamemnon".
In another it's labeled a "Supercarrier."
upsized, wrecked version appears in the Karos Graveyard in
Mission 08. It is referred to in the game files as "Big