In the latest issue of Empire magazine, director Zack Snyder discusses the reason as to why he chose to use Doomsday in Batman V. Superman: Dawn of Justice and what is Lex Luthor's (Jesse Eisenberg) connection with Wonder Woman (Gal Gadot).
"To go up against heroes like Batman and Superman, we wanted to introduce one of the DC Universe's most iconic and powerful villains," Snyder said of the beastly creature known as Doomsday. "He is essentially an unstoppable force. He poses a real threat to the world within the film."
From the trailers we can see that Lex Luthor plays a major role in the creations of Doomsday. The research that leads up to that experiment will draw Wonder Woman's attention. "You learn pretty early on that Lex is interested in metahuman existence," Snyder offered, "and that there might be some relationship between that investigation and the appearance of Diana Prince."
In Batman v. Superman: Dawn of Justice, fearing the actions of a god-like Super Hero left unchecked, Gotham City’s own formidable, forceful vigilante takes on Metropolis’s most revered, modern-day savior, while the world wrestles with what sort of hero it really needs. And with Batman and Superman at war with one another, a new threat quickly arises, putting mankind in greater danger than it’s ever known before.