In full, his name is Tristangrascalaticrunagore.
In spite of his membership in the Lords of Judgment, he ordinarily held himself aloof from the other gods, experiencing mutual dislike.
His reputation for human sacrifice extends particularly to his worshippers. Therefore, he never had a large number of followers.
Later, when Tri'nagore allied with Kâna, Tri'nagore used his powers to prevent witchcraft from working properly for those witches in the service of the Dragaeran Empire. This act of war, along with Morrolan's long-suppressed desire for revenge, inspired Morrolan to travel to the villages where Tri'nagore was worshipped and slay many of the inhabitants (dedicating their deaths to Verra). Morrolan then desecrated Tri'nagore's altar. When Tri'nagore appeared in response to this desecration, Morrolan attacked him using Blackwand. Since Tri'nagore's physical manifestation was thirteen feet in height and "little less" in breadth, this attack must have required no small act of bravery on Morrolan's part. Morrolan and Blackwand eventually defeated Tri'nagore utterly.
Tri'nagore was subsequently judged by the other Lords of Judgment for his part in trying to overthrow the Empire, but his punishment was left at that already physically imposed by Morrolan.
After the events described above, we don't hear much about him anymore, but he reputedly has some small number of worshippers in his own world, presumably on another plane of existence, and so can still manifest there.