The Akaviri were tsaesci, immortal vampire snakemen from the uttermost east. Their defeated invasion force, spared in return for the promise of eternal service, was the root of Reman's victories. Their superior training, swordsmanship, and knowledge of eastern tactics and logistics caused sweeping reforms in the structure and composition of the Legions, making it far superior to other Tamrielic forces at that time. It is said that a skilled Akaviri swordsmen, knowledgeable in tsaescence, cannot die unless killed in honorable combat. After the fall of the Second Empire, many were trapped between their sense of honor and the last commands they received, which were "remain at your post until further notice". Now, the few remaining Akaviri reside deep in the tunnels of their fortresses, preying on unwary investigators for sustenance.
For the model, we can adapt Antares' Medusa creature (or Ashtaar's Harvester from the Doors of Oblivion mod)