The Starfire Wheel is located in the Temple of Varenni on Minbar. The device dates back to the time before Valen arrived, and was used to determine matters of dominance among the castes before the Grey Council was formed. The idea was to prevent unnecessary bloodshed by instead challenging the convictions of the leaders of the disputing castes in a trial by ordeal. Any leader can send others to die in battle for them, but only the greatest leaders are willing to give up their own lives.
The device itself is an energy projector mounted to the temple's ceiling. It is normally concealed by an aperture that can be opened to varying degrees. Once the aperture begins opening, a beam of energy is projected to the floor in the center of the temple, in an area ringed by rocks. The two opposing leaders would walk into this circle of rocks and be subjected to the beam's intense energy. As the aperture continues opening, the energy becomes more and more intense and difficult to bear. When the aperture fully opens, the beam will instantly incinerate anyone standing in the circle before closing again. A leader lacking a strong conviction will flee the circle and show his cowardice: proving him or her unfit to lead, whereas a leader who sacrifices him or herself in the Starfire Wheel will resolve the dispute in favor of his or her caste.
In a clever manipulation, Delenn and Neroon contrived an end to the Minbari Civil War of 2261 by having the Religious Caste surrender to the Warrior Caste in the Temple of Varenni, allowing Delenn to use Shakiri's desire to return to the days before Valen and invoke the Starfire Wheel. There, she showed Shakiri's cowardice and her own devotion, but it would be Neroon who would make the ultimate sacrifice. He removed Delenn from the circle and took her place, but not before converting to the Religious Caste and granting power to Delenn. As he had been a Warrior only moments before, he ensured that both a Warrior and a Religious Minbari died in the Wheel.