The Triwyrm

Pathfinder

Chaos (Whimsy)
Scalykind (Dragon)
Earth (Caves)
Liberation (Freedom)
Knowledge (Education)
Plant (Growth, Decay)
Death (Murder)

5e

Death
Knowledge
Nature

As there are three heads of the Triwyrm, there are three holy books.

Kralvan-Dristh

Mavrinos's "The Book of Blood" is a dark book describing the glory of afterlife as a dragon in Roldkorfell, and how those worthy become them. It also details the afterlife as a Glory-watcher of Mavrinos, promising safety and dark revelry. The book instructs worshippers to cause carnage and death as though they were a dragon in life, so that they may be born anew in a body worthy of their destruction.

Lox Fretkar Ka Prakil

Also called "Five Parts of Perfection", Prasinias's holy book is a tome dedicated to the instruction of the perfection of oneself. It describes the five parts of a person that makes their whole, and how the perfection of these personal aspects leads to the perfection of the soul, allowing transcendence of the physical form, which is potentially not draconic, into the form of a dragon in Roldkerfell. The five parts of perfection are as follows; The body must be trained, and its limits pushed, so that one can reach physical perfection. The mind must be seek knowledge, so that it can reach mental perfection. One's morals must be unfaltering, whether they be righteous or insidious, so that their decisions can be perfect. Speech must be clever and quick, perfection of the social self is important. Finally, one must master a skill, perfection is useless without application, and skill is application of form. Prasinias's tome is by far the largest out of the
 

Hilvhar Dov

Draconic for "Self Importance", Chalsos's tome of worship doesn't focus much on the afterlife, instead being about mortal life. The Hilvhar Dov mostly instructs the worshippers of Chalsos to enjoy their life and make the most of it. It tells them to enjoy good company, good stories, good activities, and good food and drink (though to do none to the point that it would be self-destructive). It makes it clear, above all else, that one's life should be one's own, and you should make decisions for yourself. Much of the book is dedicated to non-religious material, such as advice regarding hosting parties, recipes, and recreational literature.

The Triwyrm is most frequently represented in iconography as a spiral of three draconic heads all reaching outwards, or as three draconic heads twisting and biting at one another.