Supreme Archon Loth of the R'Kaal
The R'Kaal are a fictitious Delta Quadrant species invented by the Doctor in an effort to disguise his attempts to steal Voyager's warp core.
The hologram of Supreme Archon Loth, a R'Kaal representative devised by the Doctor, depicted it with a pinched face with flattened features and brownish skin.
Their technology was supposedly decades ahead of the Federations, possessing such advancements as transphasic warp drive, multi-spectral cloaking systems.
They were supposedly ecological extremists who had outlawed warp travel in their space and were decades ahead of the Federation technologically.
The Doctor claimed that when they confronted the Delta Flyer and learned of the existence of Voyager, the R'Kaal's instructions were that they were to either forfeit their warp core or face destruction.
The Doctor's fabrication of the R'Kaal was later discovered by Ensign Harry Kim in the course of his investigation. (VOY: "Renaissance Man")