Here is a list of mythical creatures beginning with this letter and I am constantly gathering information from each continent and continually updating.
Arimaspi (Greek)
The Arimaspi (also Arimaspians, Arimaspos, and Arimaspoi) were a legendary tribe of one-eyed people of northern Scythia who lived in the foothills of the Riphean Mountains, variously identified with the Ural Mountains or the Carpathians. They warred constantly with the gold-guarding Grypes (Griffins) of the mountains. According to Herodotos their name was derived from the Skythian words arima "one" and spou "eye".
The Arimaspoi may be the same as the Arimoi tribe mentioned briefly by the ancient poets Homer and Hesiod. Homer also mentions a similarly named Skythian tribe, the Kimmeroi, in the Odyssey. All tales of their struggles with the gold-guarding griffins in the Hyperborean lands near the cave of Boreas, the North Wind (Geskleithron), had their origin in Arimaspea, the lost archaic poem of Aristeas of Proconnesus.