Wong was a part of Doctor Strange, where he proved to be a treasure trove of knowledge. He also was one of the sanctums of Earth, and since Strange may be making multi-verse journeys, he would be a definite guardian for Earth.
The character who started it all. From his first appearance, Thanos was teased as being a major player in the Marvel universe. His time will finally be revealed as he seeks the Infinity Stones to destroy half of the Marvel Universe.