"Well, at the moment of our deaths, Tirion Fordring -- the paladin and wielder of Ashbringer, who'd been there with us but got frozen in an ice block right at the start of the fight -- smashed Frostmourne, and all the souls that the Lich King had imprisoned in it escaped. They pinned him down, Terenas Menethil resurrected us, and we beat the holy hell out of him."

Was that an entirely-too-simple explanation?