He is the son of Nyx ("night") and Erebus ("darkness"), and twin brother of Hypnos ("sleep").
Notable Stories Involving Him:
He is considered the personification of Death, though is often overshadowed by Hades. He is sometimes depicted as an adolescent holding an inverted torch (which represents an extinguished life) in one hand and a butterfly or wreath of poppies in the other; however, he is also said to be winged, dressed in black, and carrying a sword. As the god of death, he guides souls to the Underworld, and can be either cold-hearted and merciless or the deliverer of a peaceful passing.
Thanatos Around the World:
His Roman equivalent is Mors ("death").
SOURCES: Greek Mythology.com, Encyclopedia Mythica, & Wikipedia