FusionDex

Whenever Starark disguise themselves as another Pokémon, they are never able to completely obscure the gems on their body. When their illusion is inevitably discovered, the gems glow in an array of colors as they revert back to their true form.

Each has the ability to fool a large group of people simultaneously. People in ancient times imagined that Starark were transformed from the reflections of stars that twinkled on gentle waves at night.