Some talk about lilith. How u fight her is u have to get key of hate,terror,and destruction. To get those keys u have to kill summoner for key of hate, countess for key of terror, and nilathak for key of destruction. Then u transmute 3 keys of each type in the cube and opens a portal to lilith durie or izual kill them and u get either diablo's horn, mephisto's brain, or baal's eye. you';ll have to get 3 of each key for a total of nine to do this. When u have all 3 body parts u transmute it in the cube and a portal opens to tristram and u fight all 3 of the prime evils. They are way harder than the hell versions of themselves even.