I'm probably 20 radiant quests in after the main quest line for the vampires reading about how I was supposed to get the Summon Durnehviir shout after defeating him. Well I defeated him the first time right before Salera's mom gives you the Elder Scroll, and beat him the second time after you leave the Bone Yard into the Soul Cairn. I didn't speak to him and ran straight to the Sail Cairn exit, I wasn't stopped by dialogue or anything, I just kept running. After revisiting the Soul Cairn, he wasn't at the location where you fight him, but someone told me there's a half-destroyed Dragon Shout wall in there that he sits on top of. Is this true, and if it is, what area of the Soul Cairn is it located in? I explored what I thought was everything but haven't come across this. I'm screwed if I can't find him now, I'm probably seven hours in after that part of the quest.

yes its on the far left i believe (facing the castle or whatever it is where Serana's mother is) and it's in one of those partially destroyed buildings

** nvm

You're only supposed to fight him once, lol. When he waits for you outside, he wants to talk.

Oh [censored]...basically I shot him with an arrow as soon as I saw him and his health bar disappeared so I just kept running towards the exit since it's so far away, and I didn't get Arvak's skull yet. Ugh, I wasn't stopped by any dialogue either, I probably got too far away by then.

You have to approch him to start the talk. He will give you the shout to summon him. You have to summon him 3 times and then just like the dragon you can call to aid you in the main skyrim quest, you can continue to call him to help you. Just make sure that the area you summon him in is hugh and empty and that you point your shout at the ground.

Found the wall, and he wasn't there. Ugh, I guess I'm just screwed. I really wanted soul tear.