Trelagism
Trelagism was a religion in Scadrial before the ascension of the Lord Ruler and the establishment of the Final Empire.
Beliefs
Trelagism was a dualist religion named after the god Trell. Trell's opposite was Nalt, and the two were believed to be brothers.
Trelagists believed that night was sacred and daylight was profane. During the night, Trelagists were able to see the Thousand Eyes of Trell (the stars) watching over them, but during the day, Nalt - jealous of the worship given to his brother - would shine his single eye (the sun) on the land, blocking Trelagists from seeing Trell's eyes.
One can speculate that their religious observances, if they had any, were at their height during the winter months, and summer months may have contained many petitions to Trell or attempts to ward off Nalt's jealousy. (See "Geography", below.)
Followers
Before the Final Empire eradicated Trelagism, it was practiced primarily by a people known as the Nelazan. Little is known about the Nelazan, themselves, but they were described by Sazed as being a "determined people", and that they mapped out the entire night sky. (Likely, it was only the northern sky and not the entire sky; see "Geography", below.) Since the stars were considered to be Trell's eyes, it is possible that the Nelazan did not name the stars in a manner that other cultures might, but rather gave stars - or constellations - names related to attributes associated with Trell.
Geography: The Nelazan were located far to the north of Scadrial, close to its equivalent of the Arctic Circle. The Nelazan resided just south of their Arctic Circle, however, as it was noted by Sazed that their winters had few hours of daylight, and their summers had few hours of darkness. (Had the Nelazan lived on or north of Scadrial's Arctic Circle, their winters would have had at least one day of total darkness, and their summers would have at least one day of total daylight.)
In Alloy of Law
Trelasigm may have diverged from its original beliefs since the end of the Final Empire. However, only one self-proclaimed adherent to the belief is encountered, so the apparent divergence could simply be a personal opinion of the worshiper, or even his interpretation of beliefs that have yet to be revealed to readers.
Whatever the case may be, Alloy shows a Trelagist that claims to worship Trell, who believes that Trell created mankind, but makes no comments regarding the Thousand Eyes, Nalt's eye, or even expresses a dislike of daylight. In addition, this character holds the belief that the ruling class should be made up exclusively of twinborn - a concept that might be unimaginable to the Nelazan. Whether or not the follower was a Trelagist is not clear, he referred to his religion as "Trellism", not "Trelagism", however he did name his god as "Trell".
Miles claims before/during his death that "the men of gold and red, bearers of the final metal, will come". Unknown if this is a personal belief or a tenant of Trellism.
Notable Trelagists
Other Notes
Trelagism was the fifth religion that Sazed offered to Vin.[2]