A species genetically engineered by the Founders.
The Vorta are a humanoid species engineered by the Founders to serve the Dominion as diplomats, administrators and field commanders. They look largely human apart from their ridged ears, have poor eyesight and little sense of taste, and are bred to be immune to many poisons. They regard the Founders as gods and are utterly loyal to them.
The Vorta are cloned. When one dies or fails, a new copy with the same memories is activated, so the same person can appear again and again. Vorta command the Jem'Hadar in the field and control them by handing out the drug ketracel-white on which the soldiers depend.
The best known Vorta is Weyoun, who represented the Dominion on Deep Space Nine and Cardassia during the war, and who returned in several clones. One of them, Weyoun 6, defected to the Federation with Odo's help before dying. Other notable Vorta include Eris, the first Vorta the station crew met, and Keevan, who betrayed his own Jem'Hadar unit to the Starfleet crew stranded with him in order to save himself.