Delta Quadrant species distinguished by a pinched face with flattened features and brownish skin. They were ecological extremists who had outlawed warp travel in their space and were decades ahead of the Federation technology-wise. When USS Voyager was discovered in their territory, it was ordered to surrender its warp core. The R’Kaal were, in fact, invented by the EMH to steal Voyager’s core for Nar and Zet in exchange for Captain Janeway’s life. (VOY: “Renaissance Man”).
See also: Supreme Archon Loth