1. Mythological creatures which descend from clouds to give battle to unicorns.
2. A contraction of narwhal: mortal enemy of unicorns, and slog: a varient of slug, meaning to hit hard.
Narwhal likely comes from the Old Norse "nahvalr," meaning "corpse-whale."
"Watch out for the Oomoos, Narslogs, and blah-blah-blah!"