After the death of his father, T'Challa reigns as King of the hidden nation Wakanda. Powered by the Heart-Shaped Herb, T'Challa also takes on the mantle of Wakanda's protector, the Black Panther!
T'Challa joined the Avengers on a tentative basis. He would be there if they needed him, however, when Wakanda needed the Panther, he would return to his home. This was made clear when Falcon attempted to have a conversation with him, but he abruptly had to return home (though he may have done this to avoid talking to Sam, after all when interviewed by Agent Coulson, he noted that Sam talked too much).
After he returned to Wakanda, however, T'Challa found that the perimeter to his kingdom had been breached. While investigating the alert, his sister Shuri informed him that Nick Fury had contacted them about the Secret War, but T'Challa only agreed to focus on that after Wakanda was safe.
Suddenly, an explosive caught T'Challa off guard, and when the smoke cleared, he found Killmonger lurking in the Wakandan jungles. The two engaged in combat, but in the end, the Black Panther prevailed.
The events of this battle were soon altered, however, in the Dark Dimension. It turns out that Killmonger was working with Ulysses Klaue, and planned to destroy the Wakandan capitol, Birnin Zana. Fortunately, Nick Fury and Doctor Strange were able to sway the course of history, and in the new world, Earth-84062, Black Panther stopped Killmonger from destroying Wakanda.