The Battle of Mount Bashenga was a confrontation between the combined forces of the Golden Tribe, the Dora Milaje, and the Jabari Tribe and the combined forces of Erik Killmonger and the Border Tribe.
T'Challa and Erik Killmonger arrived at Warrior Falls in accordance with tradition. Due to being stripped of the Heart-Shaped Herb, T'Challa quickly found himself outmatched by Erik Killmonger's military training and experience and although T'Challa managed to cut Killmonger once, but was ultimately beaten and left badly wounded. Killmonger decided to finish off the king by throwing him over the falls and declared himself the new king, to everyone's displeasure.
The Jabari Tribe had found T'Challa in the freezing rivers where they fish and brought him back to their domain. Nakia, Ramonda, Shuri, and Everett Ross, having escaped while Killmonger consolidated his power. With T'Challa comatose and stabilized only by the surrounding snow, Ramonda remembered to use the one Heart-Shaped Herb they stole to bring him back. T'Challa declared his work wasn't done yet and woke to the relief of his loved ones. T'Challa thanked M'Baku for saving his life and requested that he and the rest of the Jabari help overthrow Killmonger. M'Baku declined, as he had already repaid his debt to T'Challa. The group left the tribe, with Shuri giving T'Challa his Panther Habit for the upcoming battle
As Erik Killmonger's agents started delivering vibranium weapons to War Dog operatives around the world, one of the aircrafts exploded and crashed, with T'Challa emerging from the wreckage. T'Challa then challenged Killmonger, stating that the Ritual Combat wasn't over. Killmonger ordered W'Kabi and the Wakandan Army to attack T'Challa. Okoye and the Dora Milaje moved to counter, and the Battle for Wakanda began.
During the fight, T'Challa fought against W'Kabi and his soldiers, and brought down W'Kabi's war rhinos. As Killmonger, wearing his own Panther Habit, defeated Okoye and two of the Dora Milaje, killing the third, Xoliswa, he turned his attention to Shuri. When T'Challa saw this, he charged at Killmonger, and tackled him, causing both to fall into the Great Mound. Okoye tried to tell W'Kabi to stop the fight but continued anyways as he had become loyal to the Killmonger. As Okoye, Nakia, and Shuri were nearly defeated, the Jabari Tribe entered the battle and fought against the Border Tribe along side with them.
W'Kabi, determined to finish, used his rhinoceros to attack M'Baku, but his beast recognized Okoye who stood right in front of him, and started to lick her. W'Kabi descended from his rhinoceros and Okoye asked him to lay down his weapon. Feeling betrayed, W'Kabi asked his wife if she would kill him. Okoye told him that she would do so without question for Wakanda and this finally caused him to realize just how twisted he had become in his aggression. Not wanting to see his people kill each other, W'Kabi surrendered and knelt down before his love, with all his tribe who followed him without hesitation.
After Erik Killmonger's death, W'Kabi and numerous members of the Border Tribe are imprisoned for opposing T'Challa. M'Baku, as a reward for aiding T'Challa in stopping Killmonger, is granted a seat on the Tribal Council. By the time of Infinity War, some members of the Border Tribe had been released or pardoned. However, the tribe was still not at full strength when called upon to battle the Black Order and their Outriders.
Through his experiences with Killmonger, T'Challa decided to end the Wakanda's isolationist nature in a cautious way by setting up a foreign aid to other countries and promote exchanges in a variety of fields. T'Challa also held a press conference at the United Nations to reveal the true nature of Wakanda to the world. A documentary focusing on Wakanda was also produced titled Finding Wakanda.