Darklings are the villains of the first of Janna N. Malcolm's Jewel Kingdom books The Ruby Princess Runs Away and its film adaptation. They are dark creatures whose goal is to take away Princess Roxanne's necklace. As their name suggests, they hate day (one even hates usage of that word).
They do take away Roxanne's necklace, but they don't keep it for long when Roxanne (along with Twitter) turns invisible to get it back.
It is shown that they fear dragons.
Their leader is Rudgrin, and so they attempt to help her take over the Jewel Kingdom's throne. That's why they steal the necklace.