The Eye of Sarnath Tetralogy comprises the second to fifth episodes of Season 2 of the 1987 animated series
An extraterrestrial spacecraft crashes onto Earth, and an extraterrestrial uses an escape pod to land in the water of a lake in the Central Park just as the turtles practice. He tells them to find the three fragments from the Eye of Sarnath before they fall into the wrong hands, and gives them a device to search for it.
The fight for the fragments between the turtles against Shredder and Baxter Stockman then begins. At the end, the searching device destroys the Eye of Sarnath.