The current Avengers Black Panther, Goliath, Quicksilver, Scarlet Witch and Vision are relaxing with Iron Man and Thor after the Squadron Supreme story of the last 2 issues. Panther tells them of his origin.
T'Challa's father was T'Chaka chief of the Wakandas. In their land is a mountain of vibranium, a metal which absorbs vibrations. Klaw came to their land seeking vibranium to power his sound transformer, and killed T'Chaka when T'Challa was a boy. The witch doctor N'Baza took over as regent, and sent T'Challa and his own son B'Tumba, T'Challa's best friend, to school in Europe and America. T'Challa excelled academically and in sports.
When T'Challa returned to Wakanda as a man to take up the chieftainship, he wondered if N'Baza would give up ruling so easily. The regent claimed there were tests ordained by T'Chaka. T'Challa had to defeat a dozen warriors. Then he had to spend the night in the temple of the Panther God.
At that time there was no mechanised jungle as the Fantastic Four and some of the Avengers have seen. But the next morning N'Baza caused a giant panther statue to rise out of the ground. Inside T'Challa found computers, and the Black Panther costume.
For the final test the regent sent him to climb the Great Plateau, to eat the heart-shaped herb that would grant him the panther powers. But after he had eaten the herb, he found AIM agents on the plateau mining vibranium. They captured him with a Sonatron, designed by Klaw. They explain that AIM intended to build an invulnerable space station out of vibranium.
Then the leader of the AIM squad revealed himself to be B'Tumba, tired of living in T'Challa's shadow. B'Tumba tried to execute his old friend, but found he couldn't do it. They both attacked the AIM soldiers, and defeated them all. But B'Tumba paid the ultimate price.
Returning to the present we hear that N'Baza has been regent again while Panther was an Avenger. But now he has died. T'Challa is torn between his three careers, as an Avenger, as a teacher, as chief of the Wakandas.