The party entered the auditorium to confront the two elven brothers, Mirdanion Henathon and Taldonion Henathon.These two had sought to harness the power of a Lich without incurring the curse of becoming an undead being. Experimenting with portals into the Plane of Shadow, the brothers fell under the power of a cursed evil plague that was also summarily unleashed upon Adron Academy and trapping them in the Plane of Shadow for several decades. 

When they got back to the Prime Material Plane, they stayed in the Academy working to harness the evil that had infested this plane. Many, many years later, after Toril was rocked by the re-merging of Abeir and the SpellPlague, a team of dwarf miners uncovered the buried Academy under tons of rock. Unknowingly, they also stumbled upon the brothers and thier minons. One dwarf,  Orin Barala, sacrificed himself by sealing the portal that the two Elves were using to further their efforts. 

Having to overcome such a sacrifice, the Liches needed to complete a Blood Magic ritual to counter the effect that Orin had upon sealing the portal. They were in the process of continuing that ritual when the party came upon them and initiated battle. The "boss" fight was long and tough, but the group ended up defeating the Liches and their minions, setting the ghosts of Adron at peace, and collecting treasure from the college's relic storehouse.