The elves needed mithril for their most advanced and powerful toys. Mithril is a magical metal that is incredibly strong and durable, making it perfect for crafting the most intricate and complex toys. The elves also use mithril to create enchanted tools and weapons for the guards and warriors who protect the North Pole. Mithril has many unique properties that make it highly valuable, and the elves were always looking for new sources of this rare metal.