So I started the quest "Beyond Dead" and talked to Valrice, then I went to kill one of the guys but died. I got mad and left the Soul Cairn, but later I decided I wanted my wolf powers back, so I talked to Aela and got back my powers.
Now I want to go back in but it won't let me. What should I do? I'm working for the Dawnguard not Harkon.
Best Answer
TL;DR:
From the wiki
Unfortunately I couldn't find any clear indications that you can become soul trapped again to re-enter. Becoming a vampire again seemed to be the only option, as Serana will no longer give you the option to become soul trapped again.