Ullr is a Night Transformer. He takes the shape of a scrawny orange tabby cat with a black-tipped tail during the day and, come night, the black tail tip spreads out to cover him, turning him into a black panther with an orange-tipped tail.
Ullr belongs to Snorri Snorrelson, although during part of some adventures, he stayed with Jenna Heap. He is a Spirit-Seer like Snorri. Snorri looked through his eyes and helped save Jenna from Queen Etheldredda.