During the Dark Exile, the Prime Evils were banished to the mortal realm by the Lesser Evils. In the mortal realm they caused widespread ruin and suffering. Eventually, the Archangel Tyrael intervened. He provided the mortal Horadrim Brotherhood three powerful gemstones known as Soulstones, capable of holding the vile demons' spirits. Now that humanity was equipped to combat Evil, the hunt for the Three began.