Soul Tear

Learn all three words of Soul Tear - a Dawnguard shout taught to you by Durnehviir, the undead dragon you meet in the Soul Cairn during Beyond Death. After summoning Durnehviir (you learn the Summon Durnehviir shout there), he teaches you a word of Soul Tear each time you call him - summon him three times to learn all three words.