Kally’s home world is actually a satellite of a large gas planet. Once every ten years the planet’s orbit takes it into the shadow of it’s parent planet. Resulting in a week long solar eclipse that has come to be known as “the great darkening”. during this time goblins, trolls and other light fearing creatures come out to commit all sorts of mischief.
In many areas it has become customary to wear disguises
In order to fool the night creatures into not threatening them.
And since the creatures are pretty dim-witted, the tactic usually works….