The battlecruisers were the equivalent of human submarines and were designed to dock with the Sea Devil colonies on the sea bed. The battlecruisers were also equipped with a particle suppressor as a defensive weapon. One battlecruiser was that of Silurian Triad member Icthar and his two companions, Scibus and Tarpok. In 2084, Icthar used it to collect the Sea Devils of Elite Group One and then attack and invade Sea Base 4. (TV: Warriors of the Deep)