I am truly, deeply horrified of tree sloths. Seriously. In the dark one night I woke up suddenly to see a crouching lumpy thing on top of my dresser and was convinced beyond all rationalization that it was a sloth, come to get me. (It was a sweater.)
Now, the more I think about them, the more they scare me. They have those flat black button eyes that never focus, they just stare. Have you ever looked at their claws? They are six inches long, and could julienne your liver with zero effort.
But the creeping slowness, the inexorable, malevolent lethargy is what terrifies me. I have nightmares where a sloth is chasing me, but there is no motion. I run and run until I'm cramping and sick and when I turn back, there are more of them, in the trees, just there. Just staring. I turn to run again and there are more all above me. They never blink. They don't look angry, or even interested. It's a passionless evil, the crouching slouching creeping sleepy sickly evil of an oil spill, or a cancer.
Sometimes I fear that one will wrap its too-long arms around me, and I will be paralyzed. The hug will go on forever, crushing the breath and the life out of me, but so, so slowly. Civilizations rise and fall and I am trapped interminably, unable to breathe, unable to lose consciousness, while the sloth looks blankly at a banana six feet away.