Unown

Carahnian Unown is one of the rarest Pokemon to ever exist, even rarer than the legendaries Razolteun and Amulteun themselves. This Pokemon takes on the form of a symbol in Carah well known for its mythological symbolism - the rising empire of Carah and the Genesis Aureole. This symbol is present in a variety of Pokemon, including every Genesis Form and every legendary. In fact, the aureoles above every legendary are some disambiguation of this symbol. It is unclear why this Pokemon took on this specific form, but many scientists have theorized that it has something to do with this Pokemon's astral origins.