It can be ascertained without a shred of doubt that Thanos had proved his claim as one of the strongest celestial ever in Avenger: Infinity War. But the backstory behind him having so much power was always shrouded in mystery- until now.
Previously, audiences got little to no information about why the main antagonist of the Avengers possessed such immense power. This has been finally deconstructed in a Marvel comic, released in 2021, which sheds quite a highlight on the Eternals, and the origin of this supervillain.
The Eternals, Thanos’ origin, and the cosmic side of Marvel
The Cinematic Universe of Marvel has always danced around the edges when it came to topics such as Thanos, the Eternals, or even the cosmic side of the uber-famous comic series. In the Guardians of the Galaxy, Gamora had once mentioned that Knowhere sat on the shoulders of an unnamed celestial.
Later, the Collector also went on to explain the Infinity stone were a Celestial came about wielding the power stone. Interestingly, Ego- the father of Peter Quill and his main villain was also a celestial himself. The origin of the Mad Titan is also somewhat similar, for he is the son of an Eternal in the comics.
The comic ‘Eternals: Thanos Rising’ shows quite an in-depth view of the parentage of Thanos. As it is well known, the Eternals are thousands of millennia old. With that being kept in mind, it is pretty evident that they would have experienced brutal battles and wars that would destroy whole planets. But for individuals with infinite power, this was just another day. In the comics, the Eternals are regularly surrounded by civil wars, which clear up pretty quickly.
Thanos comes into being because of an anomaly- for Eternals usually cannot have children. However, A’Lars and a Titanian woman want to start a family, for which they turn to the titan Kronos- which leads to them having a child of their own, who grows up to the mad Titan himself.