The pantheon is not a family of allies. It is the record of a single choice, made once, under fire, and never undone. When the Fallen tapped the Void and the war began, every god chose, and the choice sorted them into three houses that still define the world. The Withdrawn kept faith and left. The Undivided refused the war and fell to mortality for it. The Fallen's Host followed him into the dark. Mortals wear these allegiances as dragon-heraldry, because each god made a dragon in its own image, and those twelve firstborn are the oldest living things in the world.
The loyal gods who kept faith and left the world by judgment, holding that their return would only resume the war that breaks it.
Gods who could not bring themselves to wage the war, even to save the world, and fell to mortality for their refusal. They still walk the dying world in ruined, human form.
The gods who followed the Fallen down into the Void, each for a reason of his own, and became the dark powers of the age.
Each god made a dragon in its own image, and these firstborn are the oldest and mightiest living things in the world. Mortals wear a dragon-sigil to declare which god, and which house, they answer to. To read a banner in the Sundered World is to know whose side its bearer has taken in a war the gods themselves have left.
Why the gods chose as they did is The Fall. The mortals who still answer to them are The Peoples, organized into The Six Orders. Meet the Undivided who walk the world in the Cast.