The Adamantine was a dreadnaught affiliated and owned by the Darksmith Collective. It's appearance of the ship is similar in shape to a cathedral. It was also able to carry a battalion of the Darksmith's soldiers, the Dreadbringers.
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)