The third god was not of Asgard, but was actually a psychopomp from ancient Greek mythology. Marvel has a history of adapting ancient religions into comic book heroes and villains. The most well known example are Asgardians like Thor and Loki (the other two gods in the film). However, many people know that Marvel also took characters from Greek mythology. Hercules is probably the most known (except for the character that appeared in Avengers), but Marvel has adapted more than 25 other Greek gods and heroes.
So who is the third god and what is a psychopomp? Well, by answering the second question most people will be able to guess the answer to the first. A psychopomp is an entity that guides souls from the world of the living to the world of the dead. Well known psychopomps include the Grim Reaper, Hermes, Anubis and if you are a comics fan Thanatos (or as Marvel calls him Thanos).
Ok, so the names aren’t exactly the same, it could just be a coincidence right? Well let me tell you a little about Thanatos. He was a minor god in Greek mythology whose most notable story comes when he is charged with punishing King Sisyphus by forcing him to roll a heavy stone uphill for eternity without ever reaching the top.
Marvel’s adaptation is pretty loose, but here are characteristics that were given to Thanatos by the ancient Greeks: He was obsessed with death, he hated and was merciless toward the living and was rarely defeated but could be tricked from time to time. Sounds a lot like a certain Mad Titan, doesn’t it?
What proves that Thanos is an adaptation of Thanatos (at least in my mind) is in 2010 Marvel introduced a new character who faced off with Hercules -- Thanatos. The comic Thanatos was a more faithful adaptation of the myth, but what this proves is that Marvel had their eye on a really obscure Greek god. There are hundreds of Greek gods or heroes to adapt and yet they chose one most people (even the ones that took mythology in high school) probably haven’t heard of.
So, who cares? Besides that it is just plain ol’ interesting, I decided to write this after seeing a few comments calling Thanos a rip-off of Darkseid. While the character designs are similar and Thanos was introduced after Darkseid, I just thought it would be helpful for everyone to know Thanos’s rich mythological history. Plus, who cares if one came after the other? They are both awesome villains, lets all try to get along :)