The Vastaya are chimeric creatures of Runeterra whose lineage contains both human blood and the spiritual magic of a pre-human race. From the ferocious, bestial power of Rengar to the foxlike allure of Ahri, Vastaya can look considerably different from one another, but they all share animal and human characteristics.

The Vastaya's origins can be traced back to a hidden corner of Ionia where a group of humans fled in escape of the Great Void War. There, these refugees came into contact with a tribe of intelligent shapeshifting creatures who were greatly in tune with the world's natural magicks. These spiritual creatures, known as the Vasthayshai'rei, welcomed the human refugees and eventually produced what Runeterrans now refer to as Vastaya – a blanket classification for any number of species of chimeric creatures. Over time, the varied offshoots began to settle in different regions and naturally adopted different forms – simian, avine, even piscine – according to the creatures which most embodied their strongest characteristics.

In addition to their animal-human forms, Vastaya are notable for their extremely long lives. Some have been known to live for thousands of years, while others claim to be immortal.

As time wore on and the Vastayan bloodline spread throughout Runeterra, an interesting genetic aberration occurred: certain humans with very small amounts of Vastayan heritage gained the ability to shapeshift. From the frozen Freljord to the darkest jungles of Runeterra, these shapeshifters can't maintain their animalistic forms for long, yet are still capable of harnessing some of their ancestral magic and change their shape.