"Authority should never be used as a club, Delenn."
- – Dukhat
Dukhat was the leader of the Grey Council for several years prior to 2245. He was held in great esteem by the Minbari people, regardless of what caste they may have been in--so much so that he was often considered to be the greatest leader of the Minbari people since Valen, his ancestor.
In approximately 2232, Dukhat brought a bright but timid member of the religious caste named Delenn to serve as an aide to one of the Council members. He prompts her to speak before the Council. He challenges her to come out of her shell and to test her own intelligence. After her insightful response amuses him and embarrasses the others, he tells her that she will be aide to him personally. Upon giving her this assignment, he orders her not to follow the usual custom of aides always keeping their eyes downcast. "I cannot have an aide who will not look up," he says, "you will be forever running into things." Many years later, Delenn would use this exact phrase and instruction for her own aide, Lennier, whom she was training as Dukhat had trained her.
Subsequently, Dukhat took the young Delenn under his wing and the two formed a strong student/mentor relationship. Duhkat trained her to follow in his footsteps with the hope that she would follow him as leader of the council. Early on in her assignment as Dukhat's aide, Delenn served as his guide and protector during the Dreaming ritual.
Dukhat was in contact with the Vorlons Kosh and Ulkesh in 2245, was hosting them aboard the Grey Council's cruiser, and held their counsel in high esteem. He kept this fact secret, even from his protégé, Delenn.
That same year, Lenonn, the leader of the Anla'Shok, appeals to the Grey Council for greater resources in preparing for the impending return of the Shadows (per the ancient prophecies). The Warrior Caste dismisses Lenonn's requests, prompting Delenn to suggest sending an expedition to Z'ha'dum, the ancient homeworld of the Shadows, to see if they have returned. Dukhat decides that the Council itself will make the journey in secret, with only a few support vessels. Along the way, Delenn is fully inducted into the Grey Council. As she takes her oath, she holds her hand near a Triluminary and it glows, confirming what he suspected about her lineage. Delenn asks him about the glowing, but before he can tell her they are called to the Council chambers. A small fleet of unknown ships have been detected following them. Delenn identifies the newcomers as being human vessels. The Warrior Caste explains they are approaching with gun ports open as a traditional sign of respect. Delenn then points out the presence of several nearby Soul Hunter ships. Dukhat orders the gun ports closed, but too late--the Earth Ships open fire. Dukhat is critically wounded. He dies in Delenn's arms, whispering to her that she is a "Child of Valen." Delenn does not hear the words at the time. She is so overcome with grief and shock at the loss of her mentor and friend she casts the deciding vote in starting the Earth-Minbari War. This was a great source of guilt for her over the years that followed. Dukhat's loss is such a great blow to the Minbari people that the entire race "went mad" and the war was a holy one to avenge him. 
Immediately following his death, the Soul Hunters attempted to steal his soul, but were prevented by the Minbari.