Dragon Age Inquisition

Nightmare Difficulty

On nightmare this is a huge pain.

There's some good tips for this. First. Make sure you're about level 16 or 17.

The team I used were as follows.

Rogue Inquisitor, using bows. A powerful bow, I used a crafted one I made, with a deamon Rune. Also taking Artificier as your specialty.

Dorian using Spirit/Electrical build.

Solas using an Spirit/Ice build

Blackwall using an Sword and shiled/Battlemaster build.

Battlemaster, allows Blackwall to target enemies from afar and pull them away from casters. Set him to defend Solas. This is because Solas does huge AoE damage if you set him up correctly. If possible, find a ring that makes blizzard more powerful or last longer. This is a great way to controll the fears that the boss spawns.

Dorian will be a bit of a pain, he likes to be in the middle of battle for some reason during this fight. Defend him as much as you can.

If one caster goes down, switch to the other. Wait for the mana to build and ressurect the other. Using the second caster ressurect to either help yourself or Blackwall up.

Blackwall must have spirit resistance to be effective during this battle. Also, any armour mods that add health will be a great bonus.

Give Dorian an Fire staff, one move from the electrical tree will be converted to fire DoT effect and burn the enemy whilst he casts electrical damage from other spells. Give Solas an Ice staff, it's pointless giving him anything else.

For Blackwall, a high-end Axe is a lot more preferable than a sword. The damage output is so much better, particularly against the boss.

At level 17, I did this first time. At lower levels it became a stumbling block and the game wouldn't allow me to pass through.

If you're still struggling, I also beat this boss by swapping out Solas woth Vivienne and having her use Spirit/Fire build. Although, this tactic may take longer to kill the boss.