Funny enough, my paladin was the only one with Devil's sight
I luckily avoided the reflect cuz the boss pretty much ran up the staircase solo and got fukking clapped in like 2 turns while everyone else either still dashing or stuck in the Hunger of Hadar at the bottom of the stairs
. The darkness fukking up my offensive range and positioning probably was the biggest difficulty of the fight despite the number of enemies.
That shyt was ridiculous at one point tho I had Jaheira action surge ice storm twice, paladin/warlock Hunger of Hadar in the same spot, and then had Shadowheart cast web. Mf's was slipping prone, getting burnt by acid at the beginning and end of each turn, and then half of them got stuck in the web so they would just keep taking damage from HoH
All that and them mf's still had me fighting for my life on that damn staircase