The Ellimist refers to the invading alien force as "the Yeerk", using it as a collective plural noun. In the books, the plural of Yeerk is always "Yeerks". See more
I am an Ellimist. Since the dawn of time, I have observed every detail of the universe. My interests have taken me far and wide, studying beings on worlds throughout the cosmos. Recently, my attention has been drawn to colorful small, blue world known as... Earth. Ruthless aliens called called the Yeerk have begun an invisible invasion, taking control of human minds, turning them into helpless slaves. And now, everything has changed. The Yeerk leader, Visser Three, gained control ...