The Kurloc, commonly misspelled as Kurlock, is a large bear-like beast with red fur and large ram horns. The Kurloc is a loyal pet to the Keeper of the Spire. He guards the spire against intruders, protecting the valuable artifacts within.
In Keeper of the Spire, the Kurloc attacked Rapunzel, Calliope, and gang on their way to the Spire vault. They eventually trick it into falling into a poison elm field so they can get into the Spire unimpeded.
When the Keeper reveals himself to Calliope, he also explains that the Kurloc is his loyal pet and he gives Calliope one as well.