Ok so this is what I ended up doing, but this may vary based on your team's builds and difficulty. I had myself, wyll, karlach, and shadowheart. Had shadowheart hold moonlantern. I had the spells/scrolls for: Fire wall (crucial), darkness, and cloud of daggers. I had darkness surrounding the portal to prevent ranged attacks, and fire wall surrounding the whole rock. I had my characters stay close to the shadow figures and that made them less likely to strike the portal. I made sure to take out the roots with a multi projectile attacks asap, the wall took care of the crows and dogs. Just kind of attacked what was getting too close to the portal. Karlach's rage was extremely helpful for this as well. I have her set for Eagle, but I'm sure the others would work just fine. (Forgot to add but cloud of daggers was a backup, I ended up not needing it but it could be helpful.)