Chaser

Quote from The Legend of Zelda: The Minish Cap Chaser figurine:

"Appears in dungeons. They move quickly to chase you once they spot you. Your shield will block them, but keep on your toes!"

In Phantom Hourglass, a new enemy known as a Chaser will stalk Link around certain dungeons. They look like Darknuts, but even one hit from its sword is fatal. There are "safe zones," however, that the Chasers cannot enter.