Moridin learned it after he had been beaten to shit by 2 Mandalorians, got stabbed by a Hapan, lost his Sith Sword, got shot several times, and then he basically after all released a massive wave of darkside destruction(destroying and disintegrating everything around him) then got up and started zombie walking his towards another enemy and on his way he started using Force Drain to recover. Then he got shot again and almost died but a Sith Master saved him. It was a LONG story.