Unnamable Horror

The Unnamable Horror was a being of incomprehensible structure that somehow found its way from the realm of Chaos into Creation in the first days. It raped the Aldar Maya, resulting in the birth of humanity and the seed of the War of Humanity. Millennia later, a mortal named Servelan de Vermiis summoned the Unnamable through an elaborate ritual and merged with it to become the Goddess of Chaos, Eris.

The being's inexpressible monstrosity is expressed in the Horror card of the Deck of Legends.