In Greek mythology, Orthrus was a two-headed, serpent-tailed dog,
a brother of monsters such as Kerberos and the Khimaira. He mated
with the latter, siring the Sphinx and Nemean Lion. His master was
the three-bodied giant Geryon, king of the sunset isle of Erytheia.
Orthrus was set to guard his master's fabulous herd of red-skinned
cattle. When Herakles was sent to fetch these as one of his twelve
labors, he slew Orthrus, the herdsman Eurytion and Geryon.
Orthrus may have originally represented the constellations Canis
Major and Minor, the two heavenly canines forming the double-head
of Orthrus. The chief star of Canis Major is Sirios, the dog star,
whose dawn rising was thought to bring on the scorching heat of
mid-summer.
(Font: Wikipedia)
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