When reaching the Pandemonium Fortress Level 2, Master Necromancer Ordan talks to the female Necromancer Celsa. He reveals that, retroactively, he trained the other masters how to guide the Wizard, Monk, Barbarian, Witch Doctor, Demon Hunter, and Crusader apprentices how to defeat Malthael. It all makes sense now how they knew something so critical, considering necromancers have better knowledge about the Balance, and how to deal with life and death.
[bluepost]Master Necromancer Ordan: At last, I have found you.
Celsa: Master? Why are you here?
Master Necromancer Ordan: We are reunited at our most dire hour. Many of our priests have fallen.
Celsa: Even you, master.
Master Necromancer Ordan: It is as it should be. I have come to aid you in defeating Malthael. You must wield a power beyond what you have ever dreamed possible. But first, you need to free us from our prison deeper in the fortress.
Celsa: I swear it will be done.
Master Necromancer Ordan: This angel commands a power beyond his understanding.
Celsa: Surely he possessed great knowledge as the Archangel of Wisdom?
Master Necromancer Ordan: Yes, but he sees virtue only in the light, not the Balance. Without some measure of harmony between both these forces, we are all lost. The victory he imagines for himself could never come to pass.
The truth is that you were not finished with your training when you left us. But I knew that if you'd stayed, you would have died in Malthael's attack.
Celsa: You said many perished. Why was I spared?
Master Necromancer Ordan: Your life serves the Balance, as it always has, but perhaps you see it more clearly now. There is still a great deal you must do before your journey ends.
Celsa: I see now! This is what you spoke of... I feel as though I am on the edge between life and death, and both will bend at my command...
Master Necromancer Ordan: You are closer to the Cycle than any of us have ever been. Use this power to bring us peace.
Celsa: You have given me a great gift, master.
Master Necromancer Ordan: I give you a challenge. Do not fail.
Master Necromancer Ordan: We studied the Cycle for years, but we did not see the extent of this disaster. There were dark portents after the Worldstone shattered. The masters spent years trying to decipher them. It was clear that something was coming.
Celsa: If only we had better prepared.
Master Necromancer Ordan: My apprentice. If we had not made these preparations, you would not be standing before me now.
Celsa: What if I had been defeated, and could not reach you?
Master Necromancer Ordan: There are many spirits here... great and small from across the lands. I have instructed them on how to aid their allies, much as I have aided you.
Celsa: Of course. You consider everything.
Master Necromancer Ordan: It is a trait I would like to see in my apprentices as well.
Celsa: When this is over, I shall return to the necropolis. Deathspeaker Jurdann will know of your actions.
Master Necromancer Ordan: That is impossible. He was one of the fallen.
Celsa: Then who leads our numbers?
Master Necromancer Ordan: You must show them the way. Ensure that our traditions survive.[/bluepost]