Not long ago, Eorzean unicorns numbered in the thousands, and could oft be seen roaming the Coerthas highlands in great majestic herds that would render the mountains white as snow. Poaching has caused the population to decline, and if it were not for your act of kindness, there would be one fewer.
Your precious horses, they're just unicorns with a big empty forehead. - Chief Chocowacker
— In-game description