Uniwhale

The Uniwhale (sometimes called the Narwhal by scientists who think the name uniwhale is silly) is a ferocious sea beast that has a long harpoon thing attached to it's head. They roam the northern Canadian coastline in search for prey. Godless killing machines, uniwhales should be avoided along with the rest Canada.

Origin
The uniwhale was created by the Canadian government in the early 1960s in order to guard and secure Canada's borders. This was done by surgically attaching the horns of unicorns to the heads of whales, a process known as unifying. The sick, twisted experiment entitled "Project: Whale With A Harpoon On It's Head" was a success and soon the waters of Canada were full of uniwhales. In the following weeks uniwhale attacks plagued coastal Canadian cities and even some parts of Alaska. Eventually the attacks became so frequent and problematic that many people decided to just leave Canada all together.

The project was officially abandoned by the Canadian government in 1989 when they realized nobody really wanted to get into Canada in the first place.

Relationship To Other Unicreatures
Since the uniwhale is a sin against nature and was created by Canadians it cannot be a true unicreature. However, since the horn of a uniwhale is actually a surgically-attached unicorn horn the existence of unicorns is 100% guaranteed. But you already knew that, because unicorns are in the Bible.