Helios

Helios is a unicorn, and the summoned mount of Heimdall.
In the era of the Ascendants, when Heimdall infused his Moonlit Shield with the heart of the slain Water Primordial, Helios acquired similar ice-centric characteristics to Heimdall. His hooves, horn, and mane became crystalline and icy, and chilly fog often emanates from him.