The Adamantine was a dreadnaught created by the Darksmith Collective. It's appearance of the ship is similar in shape to a cathedral. Like other ships of this class, it was able to carry a battalion of the Darksmith's soldiers, the Dreadbringers.
Biography
The Darksmith High minister Drakon ordered the the dreadnaught to pursue the Doctor after escaping with the Eternity Crystal. (PROSE: The Colour of Darkness)
The ship managed to chase the Doctor to the frozen planet of Flydon Maxima. (PROSE: The Depths of Despair) It later caught up with the Doctor again on Orbit Station 3, where they successfully captured the Doctor. PROSE: The Planet of Oblivion) The ship then carried the Doctor back to Karagula, where he would be placed on trail, like the Doctor arranged it, by the Shadow Proclamation. (PROSE: The Pictures of Emptiness)