List all divination systems

Public, unauthenticated. Returns the full system catalogue — id, name, tradition, endpoint, TIAN Points cost, description, and icons. This is the canonical, always-current machine-readable index of every endpoint. Note on iconVariants: white and black are monochrome ALPHA-SILHOUETTE tints (constant white/black RGB with the artwork in the alpha channel) intended for compositing over a contrasting background — previewed on a matching background, or with alpha ignored, they look like solid squares; transparent is the full-colour tile that works on light and dark alike.