Thanatos is personification of death and mortality in Greek mythology. He is commonly known as a harbinger of peaceful death, bringing the eternal sleep of death to the world while more violent gods were responsible for harsher death.
This card has 50 more ATK than both "Unicore" and "Ragin" and 50 less DEF than the average of the DEF of "Unicore" and "Ragin".
"Fableds" (魔轟神) basically have the name "god" (神shīn), which is probably why it's named after a Greek god. (Not a god though, minor figure in Greek mythology.)
This card also depicts Gludd, Gree and Malice, the imp-like creatures that appears in the artwork of "Unicore" and "Ragin". Amusingly, they are NOT subject to the "Lswarm" infection and are shown trying to "win back" "Ragin" and "Unicore"– even wearing pots and silverware in an attempt to look infected.