Honour mode advice: reaching final fight for the first time

I would like any advice you have for the fight against the elder brain. I’ve never made it this far in HM and Im scared of losing at the very last fight, I’ve made it so far

Details (if it helps): My durge is a level 12 circle of the moon druid, I have scrolls for summoning elementals for my companions.

My strongest party is with Laezel and Karlach, they deal heavy damage. Shadowheart provides summons on her own and much needed control spells and healing spells. We have a couple barrels of smokepowder in inventory. Lots of healing potions. Everyone has good armour and therefore high AC.

Thats the current state of my party. Any final advice before I jump in would be appreciated!