As a justification of his ban of Dorje Shugden, HH the 14th Dalai Lama often quotes Trichen Ngawang Chokden:
"Trichen Ngawang Chokdhen was the root guru of the 7th Dalai Lama and an extremely great being. He was from Amdo, so we are from the same region of Tibet, and became the first Reting Rinpoche. He was really an incredibly great being. It was he who was responsible for making Gyalchog Kalsang Gyatso what he was. These two, both Lama and disciple, had great devotion for each other. I am moved to tears, particularly when I reach the point in Gyalchog Kalsang (Gyatso’s) biography where Trichen Rinpoche says he doesn’t want anything except Reting. When the time came for him to leave for Reting, Gyalchog Kalsang requested him to stay a little longer. But, Trichen Rinpoche says, “Now, I will go”. Then Trichen Rinpoche mounts his horse and sets off. According to past accounts, there was a place in the Potala called the Wanglatang. That’s where Trichen Rinpoche left from and as he began his descent, Gyalchok Kalsang watched after him from the window of Wanglatang. It is really moving, because they both wept.
Anyway, I have been wondering what we might find in Trichen Ngawang Chokdhen’s biography. There is one by Changkya Rolpai Dorje"
Well, no reason to wonder anymore, here is what Changkya Rolpai Dorje wrote and that is often mentionned by HH the 14th Dalai Lama as a "proof" that Dorje Shugden is an evil spirit:
"An evil monk spirit (rgyal.'gong) from Dragsob (brag.sob) who was invoked by some active Lama retired from his monastic office (bla.zur) and a Khamtsen at Ganden. They built a wayside shrine for this spirit in the circumambulation path of Ganden. Trichen Ngawang Chogden declared this unsuitable. He said that since the time of Je Tsong Khapa and his disciples no worldly spirits were worshiped at his [Ganden] monastery and that in future this would also not be permitted. When that spirit was invoked through an oracle, he said that since the Trichen Rinpoche had said this, he had no choice but to leave and he excused himself and left for Taktse-Shöl. The Lama retired from his monastic office who had relied on that evil spirit died soon after as punishment by Kalarupa [one of Je Tsong Khapa's protectors]." (Ursula Bernis research)
This is the passage of Trichen Ngawang Chokden's biography to which HH the 14th Dalai Lama makes systematically reference to as something written that is related to "Dolgyal".
However, it is clear that this passage refers to Tagtse Gyalpo, a spirit of the Tagtse estate, which is not far from the Ganden monastery. The Samlo department of Ganden monastery took over this estate, and with it, adopted that spirit of the estate as a protector deity of the department. It was then worshipped in the Ganden monastery in their department for some time, until it was expelled by the great master Trichen Ngawang Chogden, who at that time was the throne-holder of Ganden. The spirit was sent back to its estate, where it was worshipped by the villagers until 1959. So it is clear, that the spirit expelled from Ganden monastery by Trichen Ngawang Chogden is not at all Dolgyal (Dorje Shugden).
It is good to know that the next incarnation of Trichen Ngawang Chogden, this "extremely great being", in the words of HH the 14th Dalai Lama, was also a Ganden throne-holder, with the name Trichen Tenpa Rabgyä. Out of his deep devotion to Dorje Shugden this master requested his disciple Dragri Choejor Gyatso to compose the first extensive Dorje Shugden ritual for the Gelug tradition, finding the first ritual composed by the 5th Dalai Lama too short.