When feeling joy, Syltoy rotates in place at a rapid rate. The rotation of its body sends out pulses of energy that induce joy in others, so the happier Syltoy is, the happier people around it will be.
Some Syltoy that were discovered in ancient ruins were found to be over a thousand years old. Ancient Syltoy are just as brightly colored as young Syltoy, so scientists are investigating what keeps their pigments from breaking down over time.