A dreadnought departing Allanor, the abandoned ancient capital of the Chodak Empire
Two dreadnoughts in the Epsion system, which was home to a Chodak outpost on Epsion II
The Chodak dreadnought was a massive type of military starship used by the Chodak Empire in the 24th century.
The Chodak of that century were the descendants of the ancient Chodak civilization that had flourished around 1,000,000 years before the Federation. Their vessels possessed mysterious technologies and capabilities, and were several times larger than a Federation Galaxy-class starship or Romulan warbird (at least a mile long), but comparable in armament. Chodak dreadnoughts were equipped with multiple energy beam weapons (unknown type) and torpedoes of an unknown type. Its most powerful weapon was the "Chodak Ray", a weapon feared by other spacefaring races.
The vessels were first observed in 2369, during the crisis surrounding the Unity Device. An unknown ship attacked Outpost Delta Zero Eight near Yajj IV, destroying it. Admiral Brodnack, Commander-in-Chief of the Chodak Star Fleet, entered Federation space, revealing the Chodak were not extinct, but a hidden remnant had survived on the far side of Romulan space. He intended to recover the Unity Device and use it to restore the Chodak Empire, but was thwarted by the USS Enterprise-D.
Later, in 2371, the Enterprise again encountered two of these formidable vessels in the Epsion star system while pursuing Doctor Tolian Soran. They may have been positioned there to defend or assist the Chodak outpost on Epsion II. (TNG video games: A Final Unity, Generations, Birth of the Federation)