The Promellians were a warp-capable technologically-advanced humanoid species. This species destroyed themselves in their long war with the Menthars. The war ended with the battle of Orelious IX in the late 14th century.
The Promellians operated advanced battle cruisers which operated at a technology level that rated as rather crude in terms of 24th century Federation technology, but were highly advanced for their time. They also used a form of information storage device called memory coils that was a crude analog of a 24th century Federation isolinear optical chips. (TNG: "Booby Trap")